On domain controllers only domain administrator users are allowed to initiate a remote desktop connection and connect successfully. In order to allow normal domain users to connect through RDP perform the below:
run local group policy editor on each domain controller
Go under Windows Settings -> Security Settings -> User Rights Assignment
edit allow log on through Remote Desktop services policy and add a user or group.
The last step is to add the above user or group to remote desktop users group on Active Directory Users and Computers -> Builtin -> Remote Desktop Users