odd video issue

I am having an odd issue with zoom video calls. 

If I am meeting with one other person, i can see myself, but not them (black screen). However, if I minimize the meeting, I can see them.  If i add another person to the meeting, I can see everyone (including the original person). If people leave and the meeting drops down to one other person only, I can no longer see them again. 

All i have tried are:

1: toggling video on and off

2. restarting zoom

Help appreciated!

3. restarting computer