Not sure if this is a Mac OS issue or Audacity issue. There are similar threads about not being able to save projects on MacOS, but my issue is slightly different. I do get the Save project dialog, but when saving to a network location nothing is actually saved. If I save to the Documents folder on the internal storage the Project will save.
If I move that Project file back to where I wanted to save it, I will get a database error when trying to open it. However, it will open in Audacity on Windows.
Looking up the database error, it seems this normally means Audacity does not have write access to the folder. But in System Preferences, Audacity does have permission to access removable storage:
Audacity uses a database manager SQLite (currently SQLite3) to manage its .aup3 project workspaces. This allows Audacity to keep everything contained within a single file.
The error “Audacity failed to read from a file in X:” can occur when a data within the database is corrupted. This particular error is somewhat of a red herring as it does not describe the underlying problem well.
SQLite performs well when the database is entirely contained on the local machine. There can sometimes be problems when the file is accessed over a network or remotely. For a discussion of these issues, see: SQLite Over a Network, Caveats and Considerations
I don’t know why you are getting the error on Mac, but not on Windows. It is possible that the database is only “mildly” corrupted but the error is being caught because of the difference in access methods between the two operating systems. If this were my situation, I would go back to my Windows machine, and perform the database repair steps.
Audacity naturally assumes it can do its most critical, important, complex jobs on whatever drive it can see. If that drive is the roomy, fast, internal drive in good health, everybody is good to go. If that drive is at the other end of a chain of internet error-detection, collision avoidance, rerouting, and packet resends, then file management will be unstable.
Your home network connection can have problems like this, too.
It is recommended you do all the work on the internal drive and shuffle files around with Audacity off.
Alternately, you can send your files off to an intermediary which “looks like” a stable drive, but then fights with the network errors without involving Audacity. Since that’s beyond most home users, we use the abbreviated form of “Always Work from the Internal Drive.”