Login Error: There has been a patch that you need to update to. (PC+Steam)

This has been happening since the start of the league.
It was fine while I was practicing for the league.

I will patch then try again. Usually the same error but the next patch usually works.

The steam downloader says 'validating files'

I googled it. Reddit came up and showed I'm not the only one.

I tried moving the installation to another SSD but the problem persists.
I tried uninstalling and re-installing. The problem persists.