If you find that the New Gallery and/or Open Gallery buttons are unresponsive, then please try the following suggestions.

Suggestion #1:

The most likely cause of unresponsive 'New Gallery...' and 'Open Gallery...' buttons is a persistent '.tempGallery' folder.
JuiceboxBuilder-Pro creates a temporary folder (named '.tempGallery') whilst a gallery is being created or edited. This folder is automatically deleted on closing JuiceboxBuilder-Pro.
However, if for any reason JuiceboxBuilder-Pro is unable to delete the '.tempGallery' folder on closing the application, then the 'New Gallery...' and 'Open Gallery...' buttons may become unresponsive the next time the program is used.

The most likely cause of a persistent '.tempGallery' folder is the use of an online synced file-sharing folder so we do not recommend saving a gallery to (or opening a gallery from) a folder being synced to an online file-sharing service such as Dropbox or Google Drive.

Even if you do not save or open a gallery from a synced location, JuiceboxBuilder-Pro stores files in the Documents folder and if your Documents folder is being synced, this could potentially cause problems, too. If your entire Documents folder is being synced, then, if possible, exclude the 'JuiceboxBuilder-Pro' inside the Documents folder from being synced.

On a Windows system, the '.tempGallery' folder is located here:

• C:\Users\Username\Documents\JuiceboxBuilder-Pro\.tempGallery

I'm not sure of the location of this folder on a Mac but if you search for '.tempGallery', you should hopefully find it.

With JuiceboxBuilder-Pro closed, please check to see if your own system has a '.tempGallery' folder in this location and, if so, manually delete it before re-opening JuiceboxBuilder-Pro.

If you do use a file-sharing sync service, try temporarily disabling it (turning off its active sync) to see if this helps.

Suggestion #2:

If you have any third-party anti-virus or security software installed, then please try temporarily disabling it (including real-time protection and ransomware detection) in case it 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 find that your security software is interfering with JuiceboxBuilder-Pro's functionality, then hopefully you'll be able to make an exception for JuiceboxBuilder-Pro in your security software's whitelist.

Suggestion #3:

The problem could be caused by corrupt data in the Encrypted Local Store (ELS) folder. Clearing this data may help.
With JuiceboxBuilder-Pro closed, please delete the following folder manually before restarting JuiceboxBulder-Pro.
Mac: /Users/Username/Library/Application Support/Adobe/AIR/ELS/JuiceboxBuilder-Pro
Windows: C:\Users\Username\AppData\Roaming\Adobe\AIR\ELS\JuiceboxBuilder-Pro

You may need to show hidden files to find the above location in Windows File Explorer.

Suggestion #4:
The problem could be caused by an administrative rights issue.
Make sure that you are using an administrator user account and, when installing AIR on Windows, right-click the AIR installation file and select 'Run as administrator' (rather than just double-clicking the file). (This is not an option with JuiceboxBuilder-Pro itself so don't worry when you don't see this option on the JuiceboxBuilder-Pro installation file.)

Suggestion #5:

The problem could be caused by a corrupt user profile.
Try creating a new administrator user account on your computer and installing both AIR and JuiceboxBuilder-Pro under this new user account.

Suggestion #6:

If none of the suggestions above help, then I'd recommend completely uninstalling and and then reinstalling both AIR and JuiceboxBuilder-Pro (taking the opportunity to ensure that both programs are up to date).
The full uninstall/reinstall procedure is documented as #11 in this forum post.
You can download the latest version of AIR from Harman's website here.

Note for Juicebox-Lite users:

The notes above refer to Juicebox-Pro/JuiceboxBuilder-Pro but apply equally to Juicebox-Lite/JuiceboxBuilder-Lite.
If you are having problems with JuiceboxBuilder-Lite, then just follow the suggestions above but replace any instances of 'Juicebox-Pro' and 'JuiceboxBuilder-Pro' in any paths with 'Juicebox-Lite' and 'JuiceboxBuilder-Lite' respectively.