Camera on but not working

[ali43]

Just spent an entire day with no outgoing camera.  The camera shows on and off and the camera light comes on when camera is set to 'on' but just shows a dark screen with a camera logo with a line through it.  (I updated zoom today and use McAfee antivirus.)  Everything else worked fine.  I have not used zoom for a considerable time. The camera worked on other apps. Zoom was activated via web browser. 

(I have noticed that when I log in to zoom it is picking up a photo from my facebook account even although I have not logged in through fbk  - is this related or a red herring?) 

Can anyone help?  Thankyou.