Please try to restore the backup to another machine to test if the issue is with a broken (missing users) backup. If the restore to a test machine also does not include users please contact the Tableau Technical Support team with a copy of your backup.
If the test environment is still running you could export all the users from Tableau Server by creating a view based on the Custom Administrative Views (the '_users' view) that can be exported to CSV. For more information please review the Tableau Server Online help documentation referenced below.
The only required pieces of information when importing the CSV file is the username and password. If Active Directory is being used, the password can be blank. If local authentication is being used, a password will need to be provided. It might be possible, depending on the local security requirements, to provide all users with the same password, and have those users change their passwords individually. The publishing rights may be easier to grant within the UI in a browser by selecting all of the users and adding the rights all at once.
The following article explains importing users via CSV:
Thanks Paul, a reinstall actually did it. Not sure what went wrong in the first backup but it's better now.
Thanks again for the assistance.