Connectivity Problem with Minecraft - Connection lost after installing NeoForge on version 1.21.1

System Information

Field Value
Operating System Linux - Debian GNU/Linux 13 on x86_64
Product AMP ‘Deimos’ v2.7.0.0 (Mainline)
Virtualization Docker
Application Minecraft
Module MinecraftModule
Running in Container Yes
Current State Failed

Problem Description

Issue

I am experiencing a connectivity issue with my Minecraft server on version 1.21.1. The server was working correctly on the vanilla version, but as soon as I installed NeoForge, the server no longer appears in the server list, and I am unable to establish a connection. I have verified that the server is online and the IP address is correct.

Reproduction Steps

  • Launch Minecraft Server version 1.21.1 without any mods
  • Confirm the server appears in the list and connection is possible.
  • Install NeoForge for version 1.21.1 and launch the server again.
  • Check the server list and observe that the server is now missing or unreachable.