Am I right in assuming that you put the
X11Forwarding yes in the
sshd config file on the server? This option just permits forwarding of X11, see
man sshd_config (see full man page):
Specifies whether X11 forwarding is permitted. The argument must be “yes” or “no”. The default is “no”.
You also need to trigger the client to setup the forwarding, e.g. by calling
ssh -X you@server.
To verify that X11 forwarding is initiated add another argument
-v to the ssh call and search for a line like
[...]Requesting X11 forwarding[...], e.g.:
you@client $ ssh -v -X you@server
debug1: Requesting X11 forwarding with authentication spoofing.
If it is working properly the
$DISPLAY variable shouldn't be empty. If it's not set, X11 won't be forwarded.