Hello @Patricia4972
I went onto your listing as a guest and I can't book your room if I put 2 people in the reservation. So at least it's working as it should be so if 2 people arrived for that 3 day reservation although your listing clearly states only for 1, then the onus is on them and you should have been paid. Did the guest cancel and Airbnb reimbursed this guest?
The fact that 2 people arrived is against your house rules surely? I would dispute this with Airbnb.
Good luck and let us know how you get on,
Joëlle