Why would you delete the admin user?..lol. Just secure it with a proper password. Some of you folks are your own worst enemy. "I have this insurmountable problem that I caused... is that the problem?".
Are you sure the user you're trying to log in with, in the openmediavault-admin group? If you have SSH access, check with the command
I would delete this user because with a user default it's more easy to get acces than if you don't know the user admin.
Maybe it is a mistake, but If I make this mistake is because I didn't knwo that will be cause problems.
However, I see that the "admin" user has not been deleted, but the password has ben changed for another user.
Thanks for a help as well!