Hi Ale_rod1500 ,
The app engineering team does not have any guidance to provide related to your Remote Desktop issue at the time as it seems mostly related to accessing session hosts via VPN using T-Mobile network which is not an issue they have seen/delt with before.
Have you filed a support request for this issue yet? Hands-on debugging with our customer support team sounds like the next best step.
Furthermore, have you looked at Remote Desktop clients FAQ | Microsoft Docs. Specifically there is a section on "VPN doesn't work" which includes:
VPN issues can have several causes. The first step is to verify that the VPN works on the same network as your PC or Mac computer. If you can't test with a PC or Mac, you can try to access a company intranet web page with your device's browser.
Other things to check:
- The 3G network blocks or corrupts VPN. There are several 3G providers in the world who seem to block or corrupt 3G traffic. Verify VPN connectivity works correctly for over a minute.
- L2TP or PPTP VPNs. If you are using L2TP or PPTP in your VPN, please set Send All Traffic to ON in the VPN configuration.
- VPN is misconfigured. A misconfigured VPN server can be the reason why the VPN connections never worked or stopped working after some time. Ensure testing with the iOS device's web browser or a PC or Mac on the same network if this happens.
How can I test if VPN is working properly?
Verify that VPN is enabled on your device. You can test your VPN connection by going to a webpage on your internal network or using a web service which is only available via the VPN.
How do I configure L2TP or PPTP VPN connections?
If you are using L2TP or PPTP in your VPN, make sure to set Send all traffic to ON in the VPN configuration.