I have two identical servers, server A and server B. If I connect to server A in Putty and enable X11 forwarding in the settings (running XMING on my PC), everything works fine. I can run all the test commands like 'xeyes' or 'xclock' and they work fine too.
However doing the exact same thing on server B results in a
Error: Can't open display: localhost:10.0
on both servers returns the same (localhost:10.0) and both servers are on the same network so the firewall rules are identical (though I'm not sure this is relevant as the commands should go through SSH)
What should I try next to get X11 working on server B?