Problem solved. Brave was disconnected from the camera device for some reason. To check this, in terminal run:
$ snap connections brave
This shows:
Interface Plug Slot Notes
camera brave:camera - -
I’ve reconnected manually. You do this by running this command in a terminal:
$ snap connect brave:camera :camera
This shows now as:
Interface Plug Slot Notes
camera brave:camera :camera manual
Problem solved.