I havent heard from the sitter. Do I still pay and book or wait to hear if they are available?

Hi if you haven't received a response from the potential sitter in 24 hours they are probably not interested. I would suggest you search for other sitters in your area and reach out to them in a booking request for your dates and services desired. And I would not click the book it now button until you and the sitter agree on dates, services and rates for the booking