Everytime I join a server, I get disconnected within a few seconds.

Each time I join any minecraft server, I get disconnected within 15 seconds. I have attached server-side and client-side "views" of this.

Redacted user is always the same username.

This happened after I updated K9 to get rid of a different bug. I have tried uninstalling K9 but the problem still persists.

I have tried reinstalling Java and deleting the .minecraft folder, still persists.

There have been similar posts but none are as detailed as this one.