I do a lot of work for customers and to do that I need remote access to their servers.
The VPN tool of choice these days seems to be Citrix Receiver.
If you are experiencing problems with FireFox i.e. you can login and get the portal but when you click on one of the icons e.g. desktop or remote desktop and you see the little wheel spin for a few moments and then stop and then nothing happens, try this:
Tools / Options / Applications
Ensure that "Connection Manager" is selected and not "Receiver".