Hello @Kittie-and-Chris0,
Is it an Airbnb coupon or travel credit and is the amount still posted on your listing?
Did you recently refer a friend to Airbnb as a guest or a host?
Coupons have a code and are awarded for in several reasons. Travel credits don't have a code and are awarded if you refer a friend to Aribnb and they subsequently travel or host someone.
If it's a coupon you should have received a message or email from Airbnb giving the code.
If it's travel credit then no code is needed and the credit will automatically show on the reservation checkout page when you next make a reservation, provided that the reservation qualifies for credit. One thing is that the price of the reservation must be US$75 or more.
Neither coupons nor travel credit can be applied retrospectively to an already confirmed reservation and they can't be used to book the new experiences service.
You should contact Airbnb if the above doesn't help to explain the problem.
How do I use travel credit
How do I use a coupon code
Contact-Airbnb-A-Community-Help-Guide
Steve.