@Tyler616 I would suggest that they do not have the app active , but send them a message by phone and repeat the message on the messaging. Inform them that you do require all guests to have a working mobile and to answer all messages both before and during their stay , be pleasant and simply send through your usual information , doubling up on the messaging . You can also add ,if this does not generate any return that they risk losing their accomodation via cancellation, if they do not respond . This usually focuses the mind. Another thing is that the guest may have booked via another booking agent or is generally a hotel guest and are simply unfamilar with Airbnb. check their reviews ... H