Many times if the guest is new to Airbnb, they jump the gun in booking as soon as they try to become a member. It can take several hours or until the next day for them to receive confirmation that all of the infomation they are providing ABNB checks out. (Verification) Assure the guest that it may take a day or so to become verified (if indeed they are new) and to check their email frequently for the confirmation. Once that happens they are free to book, and you will be seeing them soon!