The bug is pretty easy to explain as it is already reported on mobile.
A few people have mentioned that they've had problems in that thread too with PC but I wanted to make a fresh thread for that to see if there are any helpful differences, etc.
As far as I'm concerned, I've tested multiple devices, multiple browsers, and multiple universes. My two main ones at the moment are Virgo and Himalia, which consistently fail to open when I attempt a login. Whatever the day, whatever the time.