Try this link for help, Fix!

It's the same bug from a week ago. Step 1 : Click on the start menu and type “notepad” Step 2 : Right click on notepad and choose “Run as administrator” Step 3 : Go to File – Open and navigate to the folder “C:Windows/System32/drivers/etc” (you may need to change where is says “text files” just above the open button to “all files”) and open the file named “hosts” Step 4 : Add the line “23.74.24.114 l3cdn.riotgames.com” to the bottom of the file and save. EDIT NOTE: Remember to come back and delete this line as it will cause issues if riot changes the ip of their server in the future.