Game Won't Open

I recently was playing and it worked fine, i came back from a trip 4 days later, open my client and click launch, the little icon appears after that and then disappears and nothing happens. My game won't open and it's very frustrating, i've been trying for like 3 hrs to get this to work looking up countless things and nothing helps. I dont know what's going on and i need help. I'm just trying to play so league of fucking legends man.