Can't query logged on users on terminal server | qwinsta.exe: Access is denied

Question

On a Windows 2016 terminal server I can't query the logged on users (even as domain administrator). In task manager the users tab is empty.

Using qwinsta.exe I get:

Error 5 getting sessionnames
Error [5]:Access is denied.

I know this may happen when I query a remote computer and AllowRemoteRPC is disabled. But here I'm logged on locally and AllowRemoteRPC is enabled.