Just installed this from TestFlight... I said I was an existing user, selected Google Drive, then upgrade to attempt to restore my purchased license. The app crashes here. :(

2nd that. I also can not restore my current password file from OneDrive. 

I uninstalled/reinstalled, same problem.

I uninstalled, installed v5 from the App Store, then reinstalled v6Beta from TestFlight and it worked. It didn't ask me to restore purchases, it just had the Pro license in place.

As my Google Drive backup was from the Mac beta, it synchronized fine.

Side note, but after setting up the Google Drive sync information, and it was syncing, the window only had a "Cancel" option. It made me think that closing it would cancel the operation. But even after the sync finished, nothing changed, so I hit cancel to make the window go away.  This could be confusing.