Well I very much doubt that because the only real issue/ glitch would have been that the dates remained blocked but since you have received the request that’s not the case here.
Since the reservation is imminent, I would suggest you phone Airbnb and they should be able to assist you in confirming the reservation as well as rectify and system issues so it doesn't happen again. Sen a message to the guest in the meantime informing them you have stumbled on a small technical problem and are contacting Airbnb to sort it out so will be able to approve their booking shortly.
Click on the link for contact options – Contact Airbnb
Hope you get it sorted.
Ama