@Michelle2167I can't say for certain, but my guess would be based on the sequence of events that the extra payment for the additional 3 guests failed. Airbnb won't pay out any money until they have all of it: they won't issue a partial payment. Really unfair to hosts, but that's the way the system works.
Their response is utterly ridiculous. I have no real suggestion except to ask to speak with a supervisor (which typically doesn't work, but worth a try) or someone else who can advise how to proceed. If no joy there, contact them on Twitter @airbnbhelp: they seem to be more helpful there.