If your client is stuck in a perma restart loop, just set back your system clock 2 days.
The loop stopped for me.
Don't forget to set it back to normal when Riot fixes it.
2 Comments
Confirmed that this is a temp fix on the issue.
It seems Riot had a scheduled patch for August 11/12 and the client tries to look for it when you load it up. But because there isn't, it can't patch. Because it can't patch, it thinks the client isn't up to date. Since it thinks the client isn't up to date, it won't let you log in.
bump for clarity