WP-Juicebox does not allow you to import a gallery from your desktop.
You'd either need to:
1. Use WP-Juicebox to create the gallery within the WordPress interface
... or:
2. Manually embed a gallery (from your computer) following the baseUrl instructions here: https://www.juicebox.net/support/embedd … ery-folder

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That said, you should not be receiving an error 403 when clicking the 'Add Juicebox Gallery' button.
Here are a few tips which should hopefully help.

(1) As the error message you encountered is a permissions error, the first thing I'd do is check the permissions on the /wp-content/plugins/wp-juicebox/ folder (and all the subfolders and files inside it).
I'd also check the permissions on the /wp-content/uploads/juicebox/ folder (where the gallery configuration files are stored).
Default permissions of 755 for folders and 644 for files should be fine.
You should be able to check and change permissions using an FTP program (such as Filezilla) or via your hosting account's online file manager.

(2) Maybe you have a security plugin which is somehow interfering with WP-Juicebox's functionality.
If you do have any security plugins installed, then please try temporarily disabling them (at your own risk) to see if this allows the 'Add Juicebox Gallery' button to function as it should.
If you find a security plugin which does prevent WP-Juicebox from functioning correctly, perhaps the plugin has the ability for you to whitelist WP-Juicebox to bypass its security measures.
I'd also extend this troubleshooting tip to all plugins other than WP-Juicebox (not just security-related plugins) just in case you find one that is conflicting with WP-Juicebox.

(3) If you use the BulletProof Security plugin, then this may be the cause of your problem and you will need to add a skip/bypass rule to the .htaccess file in your root directory as follows:

# Juicebox skip/bypass rule
RewriteCond %{REQUEST_URI} ^/wp-content/plugins/wp-juicebox/ [NC]
RewriteRule . - [S=13]

(4) Please check all .htaccess files on your web server (there may be one in your root directory and also perhaps in your WordPress directory) for any entries which might be causing a problem, such as:

<Files *.php>
    deny from all
</Files>

If you find such an entry, either comment it out or remove it.

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If none of the above suggestions help, then all is not lost.
You can still create a gallery on the 'WP-Juicebox -> Manage Galleries' page.
After creating a gallery here, copy the shortcode presented to you and paste it into a Gutenberg 'Shortcode' block in your page where you'd like the gallery to appear. You'll find the 'Shortcode' block in the 'Widgets' section.

Once the gallery shortcode has been added to the page, you'll need to add images to your gallery.
A WP-Juicebox gallery displays all images attached to the page containing the gallery shortcode. You can attach images to a page as follows:

1. Click the 'Add Block' button (the '+' icon) to add a new Gutenberg block to your page.
2. Select a 'Gallery' block. (You'll find it in the 'Media' section.)
3. Click the 'Media Library' button within the 'Gallery' block.
4. Drag and drop the images that you want to attach to your page (i.e. the images that you would like to be displayed in your WP-Juicebox gallery) from your hard drive into the media window.
5. Wait until the images have finished uploading.
6. Reorder the images (if necessary) by going to the 'Create Gallery -> Media Library' section (within the media window), selecting 'Uploaded to this post' from the drop-down menu and then dragging and dropping the thumbnails into the order you require.
7. Close the media window via the cross at the top right. (Do not click the 'Create a new gallery' as this will create a native WordPress gallery in addition to your WP-Juicebox gallery.)
8. You can now safely remove the 'Gallery' block from the page. (Using a 'Gallery' block is just a convenient method of attaching images to a page.)

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If you want to upload a gallery from your computer and embed it into your WordPress site, then you'll need to do so manually (bypassing WP-Juicebox).
I would recommend using the baseUrl method of embedding documented here: https://www.juicebox.net/support/embedd … ery-folder
Essentially, once you have created a Juicebox gallery on your computer with JuiceboxBuilder-Pro, you would upload the complete gallery folder to your web server and paste the baseUrl embedding code into the body of your WordPress page or post. It does not matter where on your web server you upload your gallery folder to as long as the two paths in the embedding code (the path to the 'juicebox.js' file and the baseUrl itself, pointing towards the gallery folder) are correct.

Here's an example (which assumes you use the current version of WordPress with the built-in Gutenberg Editor).

(1) Create your gallery with JuiceboxBuilder-Pro and save it to a new empty folder named "my_gallery_folder".

(2) Upload the entire gallery folder (not just the contents) to the root directory of your web server (using an FTP program such as Filezilla).

(3) Create a new Custom HTML Gutenberg block in your WordPress page or post (in the 'Formatting' section) and paste the following embedding code (changing the gallery dimensions and background color if you like):

<!--START JUICEBOX EMBED-->
<script src="/my_gallery_folder/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        baseUrl: "/my_gallery_folder/",
        containerId: "juicebox-container",
        galleryWidth: "100%",
        galleryHeight: "600",
        backgroundColor: "#222222"
    });
</script>
<div id="juicebox-container"></div>
<!--END JUICEBOX EMBED-->

The leading slashes in the paths above denote your root directory so the code above will work without modification as long as your gallery folder is named "my_gallery_folder" and has been uploaded to your root directory.
You can replicate this process as many times as you like (for other galleries).
Of course, for subsequent galleries, you'll need to change the name of the gallery folder (so that each gallery folder has a unique name) and change the two instances of the folder name in the embedding code, but that's all.

I hope my notes above help.

I'm not sure what that is... JuiceboxBuilder stores the Gallery Title (entered on the Customize panel) as an entry in the gallery's 'config.xml' file. There should be no file inside the gallery folder with the Gallery Title as its filename (and with no file extension). I don't even think it's possible for JuiceboxBuilder to create such a file.

Looking at your screenshot, as long as your gallery folder contains a valid 'config.xml' file (which won't show up in the 'Select Gallery Folder...' dialog), the gallery should open if you just click the 'Select Folder' button (as your gallery folder has already been selected in the screenshot).

I think I'm going to need to get hands-on in order to troubleshoot your problem further.
The instructions here really ought to work fine: https://juicebox.net/forum/viewtopic.php?id=5191

Please zip your gallery folder, upload it somewhere and provide a link so that I can check it out and see if I can replicate your problem. (This would also allow me to investigate the strange 'Trial 1000' file.)

In the meantime, try temporarily disabling any anti-virus or security software that you might have installed in case this is somehow interfering with JuiceboxBuilder's functionality. (Please do so at your own risk and be sure to disconnect from the internet first.)

Your gallery looks very similar to me in Firefox, Edge and Chrome (with just minor differences due to different browser toolbars). (I have tested both the Expand Gallery button and the Hide Thumbnails button. I don't see any major differences between browsers on my Windows 11 PC.)

If you are seeing significant differences between browsers, then try clearing your browser caches before reloading your gallery's web page in case you have made any changes and your browsers are caching older versions of your gallery.

If clearing your browser caches does not help, then please provide screenshots of the problem so that I can at least see the differences in browsers that you are seeing. I'm not sure if I'll be able to help (or explain why you see what you are seeing) but being able to see screenshots of what you are seeing might help to troubleshoot your problem.
Thank you.

WP-Juicebox comes bundled with Juicebox-Lite.
You'll need to upgrade the plugin to Pro following the instructions here: https://www.juicebox.net/support/wp-juicebox/#pro

Please note that upgrading to Pro will mean that your galleries are Pro (not branding and no image limit) but the plugin's interface will still only have Lite options. You'll need to enter Pro options as noted in the link above.

After editing a gallery, you usually just need to re-upload your gallery's 'config.xml' file (and any new images in the 'images' and 'thumbs' folders). You might need to clear your browser's cache to see the changes afterwards.

If this does not help, then please try to explain your problem in greater detail and I'll do my best to help you out.

Please take a look at this forum post entitled "Instructions to open an existing gallery in JuiceboxBuilder": https://juicebox.net/forum/viewtopic.php?id=5191

Hopefully it will help.

@willS

Was it working OK prior to this morning? If so, can you think of anything that changed on your system between it last working and just now (any AIR or operating system or anti-virus program updates)?

First of all, please ensure that you are using AIR v33.1.1.744 (links in the post above).
If you are using v50.2.1.1 (or any version after v33.1.1.744), then please uninstall your current version first before installing v33.1.1.744.

Also, try temporarily disabling any third party anti-virus or security software that you might have installed in case this is somehow interfering with JuiceboxBuilder's functionality.
(Please do so at your own risk and be sure to disconnect from the internet first.)

Until you get things working again, it would be wise to save each new gallery to a separate folder (with a unique name). Create a new empty folder for a gallery first (before opening JuiceboxBuilder-Pro) and then point towards it on the 'Publish' tab (assuming you can get that far into the process).

Unfortunately, there's no screenshot attached to your post. Try attaching the screenshot to a new post or, better yet, upload the gallery and provide a download link so that I can see the problem live on your web server (or maybe copy and paste your gallery's configuration options from the 'config.xml' file so that I can create a test gallery using your settings and hopefully replicate the problem).
Once I'm able to see or reproduce the problem myself, I should hopefully be in a better position to help.
Thank you.

Can you check your server error logs (or check in with your web host) to try to find out more about the error 500?

Also, it might help if I could see the site in question so please post the URL to your site (or email it to me at steven@juicebox.net). Thank you.

In the meantime, as you are experiencing two different errors (the admin error and the image upload error), it might help to refresh your Showkase site.
Try reinstalling Showkase. Essentially follow the upgrade instructions (https://www.showkase.net/support/upgrade/) but with the same version of Showkase that your site currently uses. If any source files have somehow become corrupt or missing, then this process will reinstate them with fresh copies.
This should not cause any further issues (and hopefully it's sort things out) but I'd recommend taking a full backup of your site as it is just now (just as a precaution) in case anything untoward happens and you need to reinstate any files manually afterwards.

Actually, what version of Showkase are you using?
If you are not already using the latest version of Showkase (v1.7.6), I'd recommend upgrading. Versions prior to v1.7.6 are not compatible with PHP 8. (See the Version History for details).

Nice!
I'm glad that you've got things working. Thank you for posting back to let me know. It's most appreciated.

Thank you for posting your troubleshooting results.
I see the problem when I "Enable HTTPS-Only Mode in all windows" in Firefox.

Here are a couple of suggestions which might hopefully help.

Try changing your embedding code to:

<script src="//www.superiorfleetbodyrepair.com/photogallery/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        baseUrl: '//www.superiorfleetbodyrepair.com/photogallery/',
        containerId: "juicebox-container",
        galleryWidth: "100%",
        galleryHeight: "1000",
        backgroundColor: "rgba(255,255,255,1)"
    });
</script>
<div id="juicebox-container"></div>

The leading double slash in the paths will inherit the protocol from the page's URL.

Failing that, try hard-coding https:// into the paths:

<script src="https://www.superiorfleetbodyrepair.com/photogallery/jbcore/juicebox.js"></script>
<script>
    new juicebox({
        baseUrl: 'https://www.superiorfleetbodyrepair.com/photogallery/',
        containerId: "juicebox-container",
        galleryWidth: "100%",
        galleryHeight: "1000",
        backgroundColor: "rgba(255,255,255,1)"
    });
</script>
<div id="juicebox-container"></div>

I hope that helps.

Unfortunately, an error 500 is a rather generic server error which doesn't really help to pinpoint the cause of the problem.

I think the best course of action at the moment would be to install and run the Showkase Server Compatibility Test.

Even if you ran the test prior to initially installing Showkase, please run it again just now in case your web host has made any changes to your hosting account recently which might somehow be contributing to the problem.
If any of the tests fail, there are troubleshooting tips on the test's support page (link above).

Please let me know how you get on.

I've just checked my email and see that you've already filled in the Download Link Request Form.
Thanks!