A Guest has contacted me becasue they are unable to book or pay. They said they they have used AirBNB many times before without this problem and they even tried a different credit card, so I doubt it is a problem with their credit card blocking the payment. They said that "When I accept your pre-approval I don't get the opportunity to instant book it goes straight to confirm booking. I have also tried another credit card." Any ideas?
Of course they have to confirm your pre-approval to get the booking instantly.
If they had chosen to Instant Book (if you have that turned on) instead of contact you for an inquiry, they would have gone straight to booking without your pre-approval. From your description of the situation it sounds more as if the problem is not with their cc payment but with their misinterpretation?