Online Proctoring - Chair required!?

I was doing a test run and the proctor said I was not allowed to work at my sit-desk because I did not have a chair. 

Has anyone seen in the rules/guidelines that a chair is required?

The proctor had full view of my environment; I could show him under my desk, where I was sitting and all the rest of my room. The proctor was also able to inspect all of my person. Why would a chair be required?

Maybe this seems a bit silly, but if i get a chair, i do not have a table at an appropriate height. Yes, I have a dining table and chairs, but those are not located in a room that I can close the door to and ensure no interuptions.