I have a backup to Onedrive for Business that has been working fine up until about a week ago. Now no files get backed up and error message is "Error occurred during backup : service unavailable.
How do I troubleshoot this?
Known issue. Some things changed on OneDrive's side after some recent updates. Our R&D is working on this, but in general we don't recommend using OneDrive of Google Drive for reliable backups.
I can suggest trying to set thread count to 1 via tools > options > advanced. If that doesn't help we need to add logs to our database, so send them via tools > diagnostic menu.