I performed the last suggestion - searched Task Manager for explorer.exe (also looked for Windows Explorer), It was not there. Entered explorer.exe at services tab as instructed (simrick). Still black screen. Then windows update popped up (shut down and install). I clicked OK and it installed, shut down, opened - completed installation, shut down and restarted again. Signed in and desktop is back
FYI - I checked Task Manager after fix and found "Windows Explorer" on the list of processes, which was not there before.
The update was KB3140768 (cumulative update).
Thank you all for your help and patience.