@Travis57
I do not know the details, but when those long-term guests had cancelled the reservation themself and Covid was the reason for it, they would have probably received all money back (According Covid cancellation terms).
You should not have cancelled the booking yourself, as you will receive "punishments" from Airbnb . Alternatevily a long term reservation can be shortened.
When subsequent other bookings were cancelled and those Covid terms apply, Airbnb would also have paid back to the guests the servicecosts charged and would have paid you some money for compensation of the lost booking. (I received it for few bookings cancelled because of Covid)
Hope this helps,
Emiel