Loading screen loads then quickly turn black

Starting on Dec 08, 2018, everything goes as per normal up to champion select. once game loads, the loading screen flashes and then quickly turned into a complete black screen. what i have tried

1. alt+tab out and in (game becomes not responding as per task manager)
2. uninstall and re-install game, not working
3. bug splat, not working

Please help. thank you.