Zoom controls disappeared on an Android tablet

I'm posting this for a friend who has a problem with Zoom on her Samsung Android tablet.  The controls have disappeared and don't appear when she touches the screen meaning she can't change to gallery view nor put her hand up to answer during a congregation meeting, it's been like this over a week.

The Samsung tablet is fully updated (and strangely her daughter who has the same tablet doesn't have this issue), and we've tried uninstalling and reinstalling Zoom from the Play Store.

Any ideas on what else we can try? BTW this is in the UK.

Cheers