Can’t verify username on Minecraft (Not a client issue)

OS Name/Version: Linux Ubuntu 22.04.1 LTS

Product Name/Version: 2.4.0.10

Problem Description:

Every time I run a Modded Minecraft instance, users NOT on my network are unable to join due to their usernames not being able to be verified.

To clarify, users, including myself are able to join when on my network, users not on my network are unable to join. And this is only when it’s a modded instance. Vanilla works


[05Dec2022 17:49:39.862] [User Authenticator #1/INFO] [net.minecraft.server.network.ServerLoginPacketListenerImpl/]: Disconnecting /[IP REDACTED]: Failed to verify username!
[05Dec2022 17:49:39.867] [User Authenticator #1/ERROR] [net.minecraft.server.network.ServerLoginPacketListenerImpl/]: Username '[REDACTED]' tried to join with an invalid session
[05Dec2022 17:49:39.869] [Server thread/INFO] [net.minecraft.server.network.ServerLoginPacketListenerImpl/]: /[IP REDACTED] lost connection: Failed to verify username!

Steps to reproduce:

  • Step 1: Make sure instance is running forge
  • Step 2: Start instance
  • Step 3: Have someone join server outside of network
  • Step 4: Causes error without fail

Actions taken to resolve so far:

I have tried to isolate every possibility I could think of.

I understand this error usually is client side so I had the user restart his instance and it caused the same issue. I also had him join a different server, it worked.

I then took the mods out of the instance and ran vanilla Minecraft version 1.19.2 and the user was able to join.

I then created a new instance to see if for some reason the one I was using was broken. The user was able to join again in vanilla but not in modded.

I then took the mods out and ran only forge, it still would not let the user join

I then copied the Minecraft instance into a folder outside of amp and ran it using the provided run .sh script and it lets the user join

I then figured it was amp causing the issue and so I did a full wipe and reinstall, completely erasing a trace of amp on my server and then doing a clean install, it still has the same outcome. All of the folder permissions are right.

The temporary fix to run my server has been to run the instance outside of amp.

This is a newer issue with Microsoft servers. Nothing AMP causes.

You can get around it by changing Disallow proxied connections to disabled. Something with the way MS authenticates users changed recently it seems.