Dynamic Queue not queueing properly

When I'm queueing up for a ranked game, I'll queue up...and sit there. Five, ten, fifteen minutes go by and nothing's happened. Now, I can understand queue times being a thing. But there's so few support players that support is practically an instant queue. To wait that long while queued as support means something's wrong. Especially because I'll cancel matchmaking and requeue immediately and get a game in five seconds. Something's causing it to sometimes not actually connect to matchmaking.