@Kathy180IMO
If you can not make the dates available again in the calender, then you need to contact Airbnb and ask them to also remove this "penalty". IMO the guests should have cancelled the reservation, as the cancelled event is not your responsibilty. If the guests made the orignal reservation already before 14 March 2020 (?), the probably could have cancelled in 2020 with full refund. And the 2021 issue is also not your responsibility. The guest could have contacted Airbnb for help (relocation ?) or you could provide manually some refund after they cancelled.