Here's how ranked works: players cant join a game in progress. You sit and wait in that lobby until the next round starts. It could be up to ten minutes.
I agree that its a silly system that only works well on consoles, and I'm sure Crytek will change that idiotic system.
But that's how it is for now. Stop leaving ranked games. Wait.
Sometimes they are just glitched and don't start though. I won't deny that. But most of the time its the first thing.