I have an issue where some external users can connect to RDWeb but when they launch a remote app, the connection never completes. If you click "Show Details" the screen is black. Normally you would see the blue logon screen (loading settings, etc.).
This only happens for random clients. Others get in just fine. To test, I used a client account from home and everything worked fine. So it has to be something with their network. I suspect port 3391 UDP is not open thought I told their IT person that port 3391 UDP and port 443 TCP need to be opened.
I have tried all the usual stuff, making sure Windows is completely updated, RDP client is updated, disabling persistent bitmap caching, changing resolution, having the user click CTRL+ALT+END (nothing happens because the session isn't established yet).
Does anyone have any thoughts on this?
Thanks!