@Laura3172
Since the CIF is highly dependent on individual host situation, I can see them not doing it right because it applies to some hosts but not others. Plymouth did implement the CIF and is one of the first towns to do so, AFAIK.
As to reimbursing guests, I would suggest providing what proof you may have of incorrect charges to Jen at DOR via desimonej@dor.state.ma.us so that they can followup with Airbnb as needed.
However, you still need to be registered and file a zero dollar return by Aug 20 IF all your July rentals were via Airbnb because of how they will report it to DOR.