@Daniel9196 This may not result in any real satisfaction for you or resolve the poor programming that has led to this guest being charged taxes for a longer than 30 night stay, but try these steps:
1. Send a letter to your local tax authority advising that the guest has been charged occupancy taxes in "violation" of rental law. Copy the letter into the AirBnB feedback tab (I have no idea how else to communicate with AirBnB CS).
2. Advise the guest that AirBnB has charged them taxes that should not be charged, are not paid to you (so you can't return the funds) and that they should take this up with AirBnB.