Payment for your rental is held whilst this is being approved. This is to make sure there are enough funds to fulfill the rental. If the rental is declined or expires after 24 hours your funds will be released back to you the following day. If your rental is accepted, your payment will be made to the lender.
If you have an approved refund, this can take up to 8 working days, depending on your bank.
If your rental is canceled, the transaction is sometimes reversed. This means the original authorization drops off your statement entirely within a few days of the cancellation. There is no payment and no refund, it will appear as if the whole transaction never happened.
If you have any questions about this, you should reach out to your bank for confirmation.