User Manager wont create new user?

[Bandito Dorito]

HI, new here, and need some help lol.

currently having an issue with the user manager. i'm trying to add a new user for a gmod server but for some reason i get either an error message saying "it was not possible to add user 'gmod server'. System message: b". " or the 'select user' box goes from my primary account to blank.

I did try using the terminal but it resulted in the system telling me the many uses for the 'user' command lol.

If this is spam i apologies, any help would be welcome, thanks in advanced.