@Missy4 Some guests simply don't bother to respond well and promptly, for which there could be several understandable reasons, so unless the booking dates are imminent, give them a couple of days- they may be on a camping trip with no internet or phone reception, they may be quite busy, maybe they don't check their email or Airbnb messages.
If the reservation is confirmed, you'll have the guest's phone number and can text or call them, alerting them to the fact that you've sent them an Airbnb message you need a response to. If you still hear nothing back, ask Airbnb to make contact with the guest.