I'm sure this is a newb question and that is why I am here lol. I have a user trying to ssh into a RHEL7 server, but gets immediately disconnected when entering his password in putty. I can't get over this issue for ONE particular user. I've looked at the /etc/shadow file and the /etc/passwd file and nothing seems out of the ordinary. I've changed his password, unlock his account with passwd -u. Changed his account expiry with change -d. I also reset his pam_tally2 with pam_tally2 --user<username> --reset. Not sure what else to do. I am not allow to change the pam.d configs. I mean, I could probably do it, but then I'd have to change them back so I don't think that is an option for me at the moment. Work fine for me and a bunch of others, just not this one person. Any suggestions? I can't restart sshd at the moment. Too many ppl utilizing the server.

My first suspicion, given everything you've already checked, would be that his PuTTY is not configured properly. That is, that the problem is with his PC, not on the server.

Can that user login from another client machine? Have you reviewed his connection settings?
Turn on session logging in PuTTY to see what PuTTY is doing.

Sean