Xmanager 4 not able to connect to Solaris11

UNIX Solaris
1

I am trying to connect via Xmanager 4 to a T4-2 server running Solaris 11.
I checked the /etc/gdm.custom.conf file.
The error I get is

The MAC (Message Authentication Code) of packet is incorrect

When I start the Xmanager on soalris I get a message
/dev/fb (file or directory) does not exist.

Any ideas

2

is a desktop installed on the server?

3

Yes and the gdm service is running. I can connect via xterm (Solaris)
Other servers running Solaris 11 I can connect to them via Xmanager. I am not sure why there is any issue with this server.