Buttons disappear

When I want to start a meeting on my labtop the buttons disappear. I use google chrome and don’t know why this happens. It makes that I can not continue. What can I do to solve this?

Yes the buttons hide after a time, so you can see better and to not bother you.
If you move the mouse and wait they will show up again.

With me they do not hide after a time, they hide immediately. When I want to start, I see the buttons one second and then they hide. So I can not begin a meeting. If I move the mouse they don’t show up.