My environment is :
1 x TS Server domain-joined Remote Desktop Session Host Role on Windows Server 2016 (Network Level Authentication enabled).
1 x APP Server domain-joined windows Server 2016 (Network Level Authentication disabled )
Both server windows firewall is disabled.
I have domain user called UserA on created DC. Both server local remote desktop users group already added.
When attempting to connect to APP server through RDP on TS Server then I got the following the error.
An internal error has occurred error.
I have checked regedit about NLA on both server.
TS Server : Y_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp SecurityLayer:2
APP Server : Y_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp SecurityLayer:2