Juicebox does not actually support responsive thumbnail dimensions. There is no configuration available which allows thumbnails to change size depending on the available space. The number of thumbnails displayed on-screen at any one time is responsive, though (see Note #2 below).

In all Juicebox galleries, thumbnails are always displayed at the designated thumbWidth and thumbHeight dimensions.
Space is reserved for the thumbnails in the gallery and the remaining space is used for the main image.

In the Top-Left Alignment demo, the gallery has fixed dimensions (1000px x 1000px) and is therefore not responsive at all. The gallery is always displayed at 1000px x 1000px, regardless of the browser window size. If the browser window is made smaller, the gallery is simply cropped.
The only way I can make anything in the Top-Left Alignment demo smaller is to change the browser's zoom setting (which affects all content on the page, i.e. the main image and thumbnails). Just changing the browser window size has no effect on the dimensions of the main image or thumbnails.

Bearing in mind that there is no way to make thumbnail dimensions responsive within a Juicebox gallery, here are some notes on gallery responsiveness and thumbnails which might help.

Note #1: Gallery Responsiveness

There are essentially two ways to make a Juicebox gallery responsive (with its dimensions dynamically changing with the size of the user's browser window).

Scenario #1:
A Juicebox gallery will be responsive (and will dynamically scale with the size of the user's browser window) if the gallery's own dimensions and the dimensions of all parent containers are expressed as percentages. If there is a fixed value anywhere up the chain, then the gallery's size will become fixed (e.g. 100% x 100% x 800px = 800px).
Please note that when using percentage heights, you may need to implement the suggestion noted here.

Scenario #2:
You could use JavaScript to listen for a change in the size of the user's browser window and assign new dimensions to the Juicebox gallery if and when this happens.
An example of this can be found in the resizable galleries support section here.
Take a look at the source of this sample gallery in your browser to see how this might be achieved.

Note #2: Number Of Thumbnails Displayed

When thumbsPosition is set to either LEFT or RIGHT, the number of thumbnail columns is fixed at the maxThumbColumns value whereas the number of thumbnail rows is variable (up to the maxThumbRows value) depending on the dimensions of the thumbnails and the space available in the user's browser.
Take a look at this demo gallery with 3 columns of thumbnails.

When thumbsPosition is set to either TOP or BOTTOM, the number of thumbnail rows is fixed at the maxThumbRows value whereas the number of thumbnail columns is variable (up to the maxThumbColumns value) depending on the dimensions of the thumbnails and the space available in the user's browser.
Take a look at this demo gallery with 3 rows of thumbnails.

@walter@web.de

Unfortunately, there is no way to show the Shopping Cart icon in Small Screen Mode. (Juicebox disables the Shopping Cart icon in Small Screen Mode as the Fotomoto window does not fit on smal-screen mobile devices.)
The only way to ensure that the Shopping Cart icon is shown is for the gallery to be displayed in Large Screen Mode (by setting screenMode="LARGE").

Maybe you could use a different Button Bar button to achieve the same effect.
If you use linkURLs instead of purchaseURLs, then the Open Image button (showOpenButton="TRUE") will open your linkURLs.
If you are already using the Open Image button (for images), then you could perhaps override a different button which you are not using (such as the Email Button).
This is not officially supported but you might like to try it.
Here's some sample code which will display the Email Button and open the corresponding purchaseURL when clicked. (It uses the Juicebox-Pro API to fetch the current's image's purchaseURL.)

<script src="jbcore/juicebox.js"></script>
<script>
    var jb = new juicebox({
        containerId: 'juicebox-container',
        galleryWidth: '100%',
        galleryHeight: '100%',
        backgroundColor: 'rgba(34,34,34,1)'
        showEmailButton: 'TRUE'
    });
    jb.onInitComplete = function() {
        $('.jb-bb-btn-email').empty();
        $('.jb-bb-btn-email').off('click');
        $('.jb-bb-btn-email').click(function() {
            var index = jb.getImageIndex();
            var info = jb.getImageInfo(index);
            var url = info.purchaseURL;
            window.open(url, '_blank');
        });
    };
</script>

You could then change the Email Button's icon to something more appropriate (see the Custom Icons support section for further details) and also change its rollover tooltip text (via the Language List configuration option).

As I noted above, overriding Juicebox's regular functionality is not officially supported and my sample code is not fully tested but it should hopefully work OK.

I hope this helps.

You're welcome! I'm glad that you've been able to change the font size of your Gallery Title.
Thank you for letting me know.

Here's a better post which describes how to change font sizes (including that of the Gallery Title).

To change the font size of the Gallery Title, just add something like the following to the foot of your gallery's 'theme.css' file (changing the values as you like):

/* GALLERY TITLE - LARGE SCREEN MODE */
.jb-area-large-mode-title {
    font-size: 48px !important;
}

/* GALLERY TITLE - SMALL SCREEN MODE */
.jb-idx-ssm-title-wrapper {
    font-size: 48px !important;
}

There's no automated way to build a Juicebox gallery using S3 images but it is possible to display S3 images in a Juicebox gallery.
However, you'd need to create your Juicebox manually (following the Manually Creating a Gallery instructions), adding an <image> entry to the gallery's 'config.xml' file for each of your images (manually entering each image's URL for the imageURL and thumbURL).

@arachnid

Good call! Thanks for sharing.

Other options to consider are MAMP, WampServer (Windows) and XAMPP.

It's an either/or situation...

If you choose to manually embed a gallery, then you do not need to use/install WP-Juicebox at all and there is no need to use the WordPress Media Library to add images to the post.

Just follow the 3 steps in the Manual Embed instructions above exactly (nothing more, nothing less) and your gallery should display in your web page.
(Upload the complete gallery folder to your root directory and paste the embedding code into a Gutenberg 'Custom HTML' block.)

Yes. The first path in the embedding code points towards the 'juicebox.js' JavaScript file (inside the gallery's 'jbcore' folder) and the baseUrl entry points towards the gallery folder.
As I mentioned in the example from my previous email, as long as you name your gallery folder "my_gallery_folder", upload the complete gallery folder to your root directory and use the embedding code exactly as I posted it, everything should work fine.
You can change the name or location of your gallery folder on your web server if you like but, if you do, then you'll need to make sure that the two paths in the embedding code are adjusted accordingly.

If you do choose to use WP-Juicebox, then you'll need to create your gallery using the plugin and use the WordPress Media Library to add images to the post. (When you open the media window to add your images, you'll likely see a 'Create Gallery' button. This refers to creating a native WordPress gallery (it has nothing to do with WP-Juicebox) which you don't want to do. All you want to do is attach images to the post so, after uploading the images, just close the media window (do not press the 'Create Gallery' button).

On a mobile device, you should be able to swipe left and right to navigate through the images.
What device and browser (and version numbers) are you seeing the problem on?
Please post the link to your gallery so that I can try it for myself.

I'm not seeing any problem with the forum software at the moment (and I log in multiple times each day).
The option to add an attachment appears for me without the need to preview.
Try completely clearing your browser's cache (or try a different browser) in case this helps.
I remember once (a long time ago now), not being able to reach the 'Register' page in the forum and clearing my browser's cache helped me to resolve that problem so it's certainly something worth trying.

You could either:
(1) Use WP-Juicebox (the dedicated Juicebox plugin for WordPress).
... or:
(2) Embed a Juicebox gallery (created with JuiceboxBuilder-Pro on your computer) manually into a WordPress page or post using the baseUrl method documented here.

(1) WP-Juicebox
You can download WP-Juicebox from its own support page here.
Instructions for use can be found on the same web page.
Just follow the first four steps in the 'Adding a Gallery' section and then scroll down to 'Adding Images From WordPress Media Library -> WordPress 5.0 (Gutenberg Editor)' for instructions on how to add images to your gallery (by attaching images to the page or post).

(2) Manual Embed
Here's an example of how to embed a gallery (created with JuiceboxBuilder-Pro on your computer) manually into a WordPress page or post.

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

Step#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).

Step #3
Create a new 'Custom HTML' Gutenberg block (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.

Incidentally, you can upload your gallery folder to anywhere on your web server as long as the two paths within the embedding code (the path to the 'juicebox.js' file and the baseUrl entry itself, pointing towards the gallery folder) are correct.

I hope this helps.

I'm glad to hear that you have ben able to resolve your original problem. Thank you for letting me know.

When opening a gallery in JuiceboxBuilder, there is no special project file to look for.
Just navigate towards and select the gallery folder itself (in your case the 'publish' folder), not a file within the gallery folder.
The gallery folder must contain the gallery's configuration file which must be named 'config.xml' (this is what JuiceboxBuilder-Pro looks for and uses to open the gallery).
Incidentally, if you have changed the structure of your gallery since saving it (and use a configUrl or baseUrl to rename or move the configuration file), then JuiceboxBuilder-Pro will not be able to open the gallery.
However, as your gallery has a regular structure and your gallery's configuration file has not been renamed, you should be able to open your gallery as follows:

I'm sorry to hear that you are having trouble with JuiceboxBuilder-Pro.

Try installing JuiceboxBuilder-Lite (from the Juicebox-Lite zip package which you can download from this web page) to see if the problem happens with both JuiceboxBulder-Pro and JuiceboxBuilder-Lite. (JuiceboxBuilder-Pro and JuiceboxBuider-Lite can both be installed side-by-side onthe same computer.)
This might help us determine whether the problem is specifically with your JuiceboxBuilder-Pro installation or with Adobe AIR itself.

The next thing I'd try is a complete uninstall and reinstall of JuiceboxBuilder-Pro.
The full procedure to follow (including a list of files to manually delete after uninstalling the application) can be found as suggestion #11 in this forum thread.
I'd also check through the list of other suggestions in the forum post in case they help.

As unlikely as it sounds, I'd also try uninstalling both JuiceboxBuilder-Pro and Adobe AIR and then installing an older version of Adobe AIR (before installing JuiceboxBuilder-Pro).
You can download older versions of AIR from Adobe's archive page here: https://helpx.adobe.com/air/kb/archived … rsion.html
JuiceboxBuilder-Pro requires Adobe AIR v2.0 or later so you could try a version such as Adobe AIR v20.0.
Here are direct links to v20.0. (All links can be found on the archive page.)
Mac: http://download.macromedia.com/air/mac/ … beAIR.tbz2
Windows: http://download.macromedia.com/air/win/ … taller.zip
If this works, then you should be able to upgrade AIR in-place afterwards (without the need to uninstall anything else).

I'd also try temporarily disabling any third-party security software that you might have installed (e.g. Avast or AVG) in case this is somehow interfering with JuiceboxBuilder-Pro's functionality. (Please do so at your own risk and be sure to disconnect from the internet first.)

If you are a Windows PC user and you know the exact time of the application crash, then you could check the Windows Event Viewer to see if there are any entries in the 'Windows Logs -> Applications' or 'Windows Logs -> System' sections which give more information on the nature of the problem.
Please see this web page for more information on the Windows Event Viewer: https://www.howtogeek.com/123646/htg-ex … an-use-it/
This might point you in the right direction.

I hope my notes above help.
Please let me know how you get on and if I can be of any further assistance.

I'm glad to hear that you've been able to resolve your problem. Thank you for taking the time to post back to let me know. It's most appreciated. I'll mark this thread as [SOLVED].

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