It is likely he is just seeing the line that asks whether he has a coupon, @Patricia715. If he has no coupon, he does not need to fill it in to continue. But payment is between Airbnb and the guest. If he continues to have problems, he will have to call the company. "Help" always directs guests to the host, so he is just following the prompts, but ultimately you cannot help him. You do not have access to his account. Tell him to google the Airbnb phone number for his area. It is the best you can do.