Dual monitor Dark screen issue

I have Ubuntu 20 (the same issue with the previous ubuntu 18) in my Toshiba Satellite l500-1UR laptop. When I plug external monitor such as an LCD screen or data show projector, the display shows dark screen with flashing mouse.

I didn’t find any driver update possibility. I changed also display’s resolution but no way!

I should mention that I am using Ubuntu beside Windows10 where I don’t have any kind of problems with dual monitoring.