connected but only see a black screen, using latest version on Teamviewer

I've used Team Viewer in the past with no problems; then, in the fall, I could no longer see my mother's screen.  It connects then I see the TeamViewer toolbar on her computer, and it's a big grayish box underneath.  She can see my cursor moving, but I can't see her screen.  If someone can assist, it would be great!  It not I'm going to have to move to another program so I can remote into my family's computer.