Problem installing on Mac

Alright so I've been playing league for a few years, but I recently got a computer(Macbook Air, Mid 2013) and wanted to play league again, so I tried installing it, and that part was fine. I dragged the icon to 'Applications', which was fine. I then double-clicked it to open it(I also right-clicked it and clicked 'Open' just in case it was something weird like that), and the rectangular window popped up(the one you get when there's an update), but this is where the problem is. The loading bar is blank, and above it just says 'Updating...", and then the ETA is 0, and the MB says '0.0 MB/ 0.0 MB'. Any thoughts on how to fix this? I miss playing Zyra and want to get back as soon as possible(I've been playing on another computer)

**I have left my computer on overnight just in case it was super slow, but I got the same result in the morning, it looked exactly the same as it did the night before.