May have the same problem as OP here. Both me and a friend of mine can queue for Warzone fine, but after an odd 5 minutes of being in queue and unable to find players, the message "UNABLE TO MATCH" is displayed.
Recruit - Iron
Made your first hot drop into HaloWaypoint.com
Halo 5: Guardians MP Beta participant.
View your Service Record on the web.
Become a member of an active Spartan Company.