Hello @Sam271,
This isn't Airbnb customer support. It's a help and advice forum where Airbnb members can help each other out from their own experience. We don't have access to anyone's Airbnb account ot trip history.
There are a few requirements for getting that credit for trips. If you satisfied the requirements and still didn't get the credit you should contact Airbnb support to find out why. They say that credits can't be applied to trips that are already booked.
To get the gredit ...
You must be a new user and you must have signed up by following the link in the email from your friend. If you signed up independently, without using the link, then you won't get the credit.
The trip you wanted to book must have a qualifying minimum cost exclusive of the fees Airbnb charged you. The "Help" section says that the minimum cost is about US$75 although this may not be the current qualifying value.
To contact support click on "Help" and then on "Visit the Help Centre" and then on the "Contact us" button near the end of the page. that will show a page with phone and message links.
You can also type "contact airbnb" in the "Search the Community" box on these forum pages where you posted your question. Scroo down a little in the llist of suggestions that appears and click on the "Contact Airbnb: A Community Help Guide[UPDATED]" one. That has phone numbers and information on contacting them via Twitter or Facebook.
To see articles on credits, type "credit" in the "Ask a question ..." box having clicked on "Help"
Steve.
