I'd ask your guest in the first instance, there might be various reasons behind a non payment - but be very clear that if airbnb can't collect a further payment, you won't receive anything either.
@Maria13440 long term guests pay in monthly instalments and airbnb now has problems collecting for the next month. Presumably, the guest has maxed out the credit card on file, card is expired and guest has forgotten to update, card has been lost or stolen etc. If you ask your guest, maybe there is a valid reason and the issue will be resolved.
Hopefully, the guest will have other valid payment methods available, but there is no guarantee.