At the office, people are able to connect to a Red Hat LINUX box and
open up a LINUX remote desktop on their windows machine. They just use
CygWin and type

$ X -query machine_name

and they then get a graphical login screen to the Redhat LINUX box.

Unfortunately, I am located outside the office and connect to the
office using OpenVPN.

I can start cygwin and am able to ping the machine. When I try

$X -query machine_name

I just get a blank gray window opening up with no login screen

Can someone give me some broad hints as to solve this problem?

Is it configuration files in RedHat LINUX that need to be modified?

Is it ports that have to be opened? If so, which ones?

Note that within the office network, everything works fine. I think
packets are getting lost when VPN is used.

thanks for any hints that you can give!