I have two servers running debian 8, and for the first time I got some strange behaviour with SSH ! On both server I got a user that can access through SSH while in LAN but when he try from WAN he got "access denied". Accessing with "root" account works well from WAN and LAN.
I have already tried the "allowTCPforwarding" option in sshd_config, just in case, but without success ...
If it could help : there is a reverse proxy to manage access from WAN, but I don't think it could be the problem as there is an other server that can be accessed in ssh and sftp by some users.
Can someone help me ?