Referral Bonus Travel credit

[Sriram-Karthik0]

I've referred my friend in Airbnb for his booking.  He got an email saying $55 off on his first trip.  He logged in with invitation successfully and post login, he see a message in notification tab as "Travel Credit not applied.  Referral credit can be only be calimed if you are new to Airbnb".  He is new to Airbnb and never logged in before, because he created the id for the very first time.  Secondly, he was not referred by anyone in the past.  Please advise, if the travel credit offer can be applied or not?