"Unspecified Error. Please check logs for more information."

So my husband and I have been having this pop up every time we try to open our League. The only option given is to hit "OK". He tried uninstalling the game and reinstalling, but it now won't even download the game at all. We both have 2012 MacBook Pros... any advice? We are unsure of what to do. I went to click on the support tab on the league website and it says safari cannot find the page.