When attempting to run a RC session against a RC Host (installed on top of a Windows 10) while it has any screen resolution in Portrait orientation like: 1024x1280, 1080x1920 or 1440x2560.
The mouse pointer can be seen moved during the RC session, but everything else is shown black:
This behavior is related to the change made in Windows 10 in regard of its video driver, where it moved from Driver to DXGI.
Client Automation - All Versions
There were some fixes released on top of 14 SP2 and 14 SP3 that solve problems and limitation caused by this video driver change, but currently for this specific issue regarding of RC session while the Host has Portrait orientation resolution, there is no solution and is not supported.