>>529180651
Well from reading several other cases and from my own testing, I noticed that the element in common that bricks the log-in is Blue Archive perceiving your connection as either too week or malicious for some reason.
I made some experiments to test this like
>using several different DNS hosts
>trying to log-in while downloading something
>trying to log-in in another wifi (nearby mcdonalds)
>using mobile data
>using USB tethering
>disabling some process in the PC that monitor connection (like other games anti-cheats)

From this testing I noticed that
>I'm unable to log-in if I'm downloading too much stuff
>I'm unable to log-in if the DNS host is saturated
>I'm unable to log-in if there's some anti-cheats active like Denuvo
>I'm unable to log-in if there's several devices connected to wifi (like in the mcdonalds during peak hours, but connection is smooth during late night)
>Mobile data always works
>Creating a tethering connection with Mobile data always works

So when I have issues log-in in, I have to follow a step-by-step protocol
>finish or cancel any downloads that we're happening in the wifi connection
>turn off any anti-cheats that we're active from playing before in the PC
>change the DNS server
>make sure that someone else connected to your wifi in another device is taking all the connection
From all this what I gather is that there's some kind of check during the log-in handshake that will block any attempts if your connection is below their designated threshold