A recent (September 2022) Windows update is causing problems connecting to Remote Desktop Services and is affecting RDS Services on Windows Server 2016, 2019 and 2022.
Remote Desktop users may see errors such as rejecting the username and password or it get stuck at “Loading virtual machine”, “Connecting to servername” or sometimes stuck as “Configuring remote connection”. In some cases, it is necessary to end the mstsc.exe task using Task Manager if it isn’t responding to other methods of closing it.
The issue connecting to remote desktop services (RDS) affects installations that use Remote Desktop Brokers and Remote Desktop Gateways.
We believe that the issue is caused because the RDS Connection is trying to connect over UDP but then not connecting over TCP if the UDP attempt fails.
If you are having problems connecting to remote desktop after installing this Windows 11 update there is a registry setting that should resolve this problem. As you’d expect we recommend you back up your registry prior to making any changes.
Open Regedit and navigate to and configure (or add new) DWORD
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\Client
KEY VALUE – fClientDisableUDP SET TO 1
Please be aware that this prevents the connection using UDP. This may potentially cause unintended consequences as UDP provides many benefits, particularly where the user has a poor internet connection or saturated WiFi connection.
If, as is anticipated, Microsoft fix the issue with connecting to RDS after Windows 11 update then you may not want to have this permanent change, so there are other fixes or workarounds that can be used.
One option is to copy the mstsc.exe and mstscax.dll from a Windows 11 21H2 machine to the same place on your machine. This may require you to take ownership of these files in order to be able to overwrite them. The assumption is with this method that future Windows updates will replace these files so you don’t have any customisations left behind in the future.
Another option which works for many people having problems connecting to RDS after Windows update is to change that logon account format. So, instead of using username@mydomain.co.uk to logon to the RDS you use the Pre Windows 2000 format aka SAM Account Name, which can be found in the Account Properties in Active Directory users and computer, and will look like: domain\username_mydomain.c as it is restricted to 20 characters
At the time of writing (December 2022) Microsoft have acknowledged that this is an issue but have not yet released a fix.