I used the code from this thread...
...to successfully filter a Wix Pro Gallery based on a user's selection from a drop-down menu. It works just how I want it to in Preview mode, i.e. all photos are displayed initially, and when a user chooses an option from the drop-down (just using "title" to get it working), only the photos with that title are displayed. When I publish, I don't see any photos to start with, and the drop-down works, i.e. I see the options, but selecting an option and pressing "Go" does nothing.
I saw a similar thread that said to sync the data (did that) and make sure dataset is read-only (did that) and make sure collection permissions are set so ANYONE can read (did that).
Here's preview mode initial state:
Here's preview mode after I choose a title and click the "GO" button:
Here is the live site initially, and after you make a selection and click "GO":
I really appreciate any help!