Can I use the original User name, but just change the password? How many login error errors trigger a disable? Will the problem clear itself after a time period, and if so, how long?
Not related to your last question, but relevant here. The login name is case sensitive, so perhaps that was the issue with the user having problems. It seems unusual to force case sensitivity on a none-password field, but that is the way it works with the admin.
You can use the same username and I believe 3 failed attempts trigger the disabling of the login. You can use the reset password file here if you ever need to https://www.ecommercetemplates.com/help/troubleshooting.asp#php6 but delte it after use.