RDP-error "The administrator has ended the session"..

Problem when using RDP-connect to a Virtual Box machine running Windows 10:
- "Your remote Desktop Services session has ended, possibly for one of the following reasons".

 Solution:
Start "gpedit.msc" (group policy editor) and change setting:

Computer Configuration -> Administrator Templates -> Windows Components -> Remote Desktop Services -> Remote Desktop Session Host -> Remote Session Environment -> Use the hardware default graphics adapter for all Remote Desktop Services sessions

Set that to Disabled on the host, and restart. It might start working for you.