I'm surprised they would allow you to run a legit BnB without being properly zoned and with a business license. It seems that Airbnb has ducked under the radar thus far but that is changing.
I would check with Air first about having to cancel due to changes of regulation. Maybe they have special dispensation on that being the issue. Then call your local municipal authority to ask about honouring bookings taken before the change. It won't look good on the town in general if guests have to cancel their plans.