Remote Desktop Connection Manager (RDCman) does not go full screen anymore

Simpler - just don't maximize the Remote Desktop Connection Manager window.

I just resize the RDCMan window to "almost" maximum size, then hit Full Screen in the RemoteDesktop connection (right click-> Full Screen).

Otherwise, it seems Windows 10 keeps a bottom bar reserved for the taskbar & doesn't allow the remote desktop to go "all the way" Fullscreen.

I know this is an old post but I had a similar problem and found that this worked:

1. Find rcdman.exe.
   Default location: C:\Program Files (x86)\Microsoft\Remote Desktop Connection Manager\RDCMan.exe
2. Open the Properties of the exe (Right click -> Properties)
3. Go to the Compatibility tab
4. Uncheck Disable display scaling on high DPI settings

Click View, then un-check Lock window size.