I recommend you isolate the problem to either SSH or the account. You can do this by SUing to the user on the system. If the user can SU, then the issue is with SSH.
Most likely something at the SSH or at the local system level is blocking the user from accessing the system.
You can get more SSH debug info this by putting sshd in debug mode via <path_to_ssh> -ddde -p 222 and having the user SSH to port 2222 and looking at the debug.