Problem solved – but let me warn you what I did wrong.
First thing I did wrong was (accidentally) try to upgrade from 18.5 (the Beta) to the regular Studio version. I didn’t even realize there was a Beta Studio version.
The main thing I did wrong was not understand the Resolve filing system. They hide the project files (which I think is stupid) so you have to use their project window to deal with project files. Make sure you do a backup before you do anything! I was told this morning that it’s a good idea to right-click on a project in the project window and choose to save the PBD file to another place on your hard drive where you can find it.
So don’t be like me – back up everything in Resolve before you do anything and make sure you stay Beta if you started in Beta.