In my personal experience, usually within 24 hours of marking it RWAP. I have had one non-response. According to the help docs, the recipient is supposed to give 5 days for the first response.
Once you have marked the book(s) received, give the sender 5 days to respond.
If you don't hear from the sender within 5 days:
For problem books that were marked received and are now in your Transaction Archive: go to your Transaction Archive and click . Then choose "The Sender has not responded." This will send an email to the sender, making it clear that she or he needs to respond or forfeit credit for this swap.
If you don't hear from the sender within 2 days after you have done the above to send that "follow-up" email to the sender, contact us. Failure to respond (in an active account) is considered admission of fault in a problem swap.
If the sender responds and resolves the problem:
You should mark the problem 'resolved' from the Transaction Archive, as described in Follow-up on Problem swaps.
'Resolved' does not require a credit refund - you can mark 'resolved' if you consider that the sender has done what was needed (even if that was nothing).
If you made an error and the swap was not actually a problem: