I've lost all my accounting filesin GnuCash in the process of "upgrading" to a new MacBook Air. Files were SAFE in Dropbox, I thought, and have been there since 2014 at least. Now I get an error code -36 from Mac trying to restore from TimeMachine. And I get nothing useful either from Code42 backups. This is a total disaster for me. The only culprit seems to be DropBox because the GnuCash data files (there were maybe 10 different sets, with multiple saved copies of the data and logs). Nothing has changed here since I last used GnuCash 2 weeks ago. And earlier today there was a swarm of notices/message from DropBox that were incomprehensible, and I ignored them for the time being. I have to do productive work here! Now the date files are gone, and I'm at wits end.
You mentioned that TimeMachine gave you a -36 error. Is that the case going back several hours or days' worth of TimeMachine backups? You may only have one corrupt Gnucash data collection, and an earlier one is functional.