League of Legends doesn't start

If I want to start a game, then I can go into the Champselect and can also pick, but if the Champselect is over, then the "League of Legends TM Client" does not open, so I can't get into the loading screen, and I also can't open it manually. (as you see in the video) On the task manager you can see that the TM client is "inactive". I have already reinstalled the game several times, reset my graphics driver settings, restarted my PC of course, and disabled the firewall. (I also have a similar problem with Overwatch)