The Qatar gov't and FIFA WC committee has blocked all rooms (most hotels have gone to media/teams/etc.), and is encouraging people to book through the qatar2022.qa accommodation platform. This is because of the extreme limitation of hotel rooms for 1.2 or so million visitors all at once. You also need a successful ticket application number to book ANY lodging, as well as the ticket number AND validated lodging to apply for the Hayya card, which will be your visa to enter the country (applicable to ALL non-Qatari nationals during the WC period). I originally contacted Hilton about it as well and they said you have to go through the FIFA and Qatar accommodation portals. Feel free to PM me if you're planning on going to the WC since there's a FB group for supporters traveling for it with all kinds of helpful info.