@Pam1620 "I was advised with Covid-19 and other uncertainties to have a no charge policy"
Advised by whom? Airbnb's computer bot? Ignore Airbnb suggestions like that, their price tips, their urging to accept last minute bookings, etc. None of that is to the host's advantage, it's just guest pandering.
Change your policy to at least moderate. The only hosts for whom a flexible policy would be okay are those who don't really care if the unit sits empty or those whose listings consistently get last-minute bookings, for instance if it is near an airport or on a driving route where people would need o'nite accommodations on a road trip.