Microsoft Windows Communication Foundation (WCF) is used for the secure communication that happens between the VDA and DDC controller servers.

WCF communication uses the computer identity for endpoints participating in the communication and presents a service principal name (SPN) with the respective computer accounts. The SPN is normally a FQDN of the host machine.

The Controller server determines the SPN for virtual desktops using the servicePrincipalName attribute of the associated computer account in Active Directory. We can inspect the virtual desktop's computer account using tools, such as Active Directory Explorer, PowerShell commands using the Active Directory module, and so on.

If you don't see any entry in the servicePrincipalName attribute for the FQDN of the VDA host machine, try editing it manually to add the required FQDN entry. This should fix the VDA registration problems.

You can view and edit the SPN attribute by using Active Directory Administrative Center...