i cannot delete plugins and when I try I get a white screen

hey. for some reason, 'Revolution Slider' has been installed twice on my system. And similar, I cannot delete it. When I try, I get a white screen and nothing is deleted.

On the bar at the top of my browser I get a long string which relates to the Envato account I have. I wonder if it's related, so I deactivated the Envato update plugin. No change.

What is the quality that causes some plugins to NOT have a delete option on the plugins page from network admin?