no loading screen

I recently went into a ranked game and i went through champ select and went through the countdown too. but when it was time for the loading screen to come on it just went to my desktop screen and was as if i never opened league in the beginning and now i got leaver buster i even tried to login again but it wouldn't work. please i need help idk how to fix it and people keep saying avast but i dont have that on my computer. SOS ASAP