Are you using AIR v51.1.1.5? If so, then this is most likely the cause of problem.
Please uninstall AIR v51.1.1.5 and install AIR v33.1.1.744 instead. Check out this forum post for details.
If this is not the problem, then have you tried creating a new empty folder on your desktop and saving your gallery to there?
Make sure that you are not trying to save the gallery to a destination that is actively being synced to an online backup or file sharing service (like Dropbox or Google Drive) and this has been known to cause problems.
JuiceboxBuilder-Pro is fully compatible with Windows 11 so there should be no problems associated with your operating system.
Out of interest, are you running Windows on an administrator user account? Have you tried using a different user account in case your current user account is somehow corrupt?
Sorry for all the questions but I'll probably need a little more information to help further. Maybe if you let me know the exact path that you are trying to save the gallery to (in the 'Gallery Folder' box on the 'Publish' tab), it might help to troubleshoot your problem.
Please let me know how you get on.