Backups triggered manually work fine. The option to create a backup on project open (File -> Options -> Backup -> Back up on project open) either doesn’t work, or is being ignored. This has been a bug since at least 2.9.0.4, perhaps earlier.
There is a separate forum for posting beta issues. You may want to request an Admin to move this post, as it’s likely not going to get seen by the right people over here.