We have recently run into an issue where changing the language on Windows 10 Enterprise Multi-Session to English United Kingdom prevents RDP access to the VM. Specifically, when copying language defaults for ‘Welcome Screen and New User accounts settings’.
The change appears to damage the Windows Defender Firewall service and prevents inbound RDP traffic (It actually blocks all inbound traffic). The issue is easily reproducible. This is preventing new AVD master images from being created (in the UK at least).