I have installed hundreds of 2016 server essentials over the years. I always go in and setup the 2 RDP administrative sessions. I recently have setup a few 2019 server essentials and did the same thing. However, I only get 1 session. When you RDP in and log in a second time it will bump out the current session.
I also have noticed Teamviewer will not connect when an RDP is active. But when I in in that RDP, I can go to the start menu and run teamviewer (because its not in the system tray) and then teamviewer will connect to that same session like a mirror (same session). I mention teamviewer just as a clue in this issue. I had no issues with this in 2016E....worked 2 RDP and the TV sessions independently. No RDP licenses, just administrative needs.
Help!