My League keeps pops up not even for a second and disappears. [Mac]

Recently, i haven't been able to play league because i just couldn't open it. It pops up for not even a second and disappears. I tried to re-install it but i can't even get on the website. It says "The webpage is not available." I know it could be my internet connection but all the other websites work completely fine. This is extremely frustrating for me and i would appreciate some help.