This is, most likely, a hostname resolution issue. On your cell manager, edit the file
/etc/opt/omni/server/users/UserList
and, temporarily add a line
"*" "*" "*" * "admin"
There is one 'space' between each field. Save the file, and see if the GUI will connect. If it does, exit the GUI, change the user list file to add the Fully-qualified domain name of your Windows system in the 4th field, which is the * without the " marks, for example
"*" "*" "*" mysys.hp.com "admin"
Save the file, see if you can connect. If not, on the Windows server, edit the file
Windows -> system32 -> drivers -> etc -> hosts
to add teh IP address and hostname of your cell manager, for example
15.111.ab.cd mycellmanager.com
save the file, and try to connect again
