Approval status - denied

Hello all, I'm new to the Community and hoping I might find an answer to my issue.

I have run a number of webinars, and notice on the post event attendee reports, that some of the attendees' approval status is showing as "denied" even though they registered and attended, and were there for the duration.  Can anyone shed any light on why this might be happening please?   The majority show as approved.

Thanks if anyone can help - it's just one of those annoying little issues I need to understand 🙂

Roz