Loading Screen won't show up after Pick and Ban Phase

Yesterday I patched the game to the newest version. The days before the 7.21 patch, everything worked perfectly fine and I played some rounds. So after patching to 7.21, I wanted to queue into a normal game. Everything seemed pretty normal, but after the pick and ban phase I was stuck on the "Game is in Progress" screen. The loading screen never showed up, even when an instance of League of Legends was showing up in the tasks. I tried it many times, through various customs but it never worked. I deinstalled and reinstalled the game, but it wasn't a solution. I also gave myself a new IP-adress and flushed my DNS but it didn't work, too. Then i looked into my firewall exceptions and saw that League should work just fine. Now I'm just sitting here, not knowing what to do. I hope someone can help me with this problem.