Troubleshooting Your Minecraft Server

Here are the most common Minecraft server issues and how to fix them. If your problem isn't listed here, join our Discord and we'll help you sort it out.

"Failed to verify username!" or "Authentication servers are currently not available"

This error means your server can't connect to Mojang's authentication servers.

For Minecraft 1.16.5 and Older

This is a permanent issue for versions 1.16.5 and older due to changes in Mojang's TLS certificates that are incompatible with Java 8.

Option 1: Update to a newer version (Recommended)

• Change your server version to 1.17 or newer, which uses Java 17+ and supports modern certificates

Option 2: Enable offline mode

• Enable offline mode to bypass authentication
• Install an authentication plugin for security, since offline mode allows anyone to join with any username

For Minecraft 1.17 and Newer

If you're on a modern version and seeing this error:

• Restart your PC and router, then try again after a few minutes
• Mojang's authentication servers may be temporarily down — wait and try again

Server Won't Start (Crashes Immediately)

If your server fails to start or crashes right away:

1. Check the Console for error messages — they usually point to the exact problem
2. Verify the server .jar file is set correctly in Startup
3. Try changing the Java version in Startup — Automatic works for 99% of cases
4. If you recently uploaded files, make sure the upload completed successfully. Use SFTP for files over 1GB
5. Check Activity for resource-related issues

Version Compatibility Issues

If mods or plugins aren't working:

• Check the mod/plugin's download page for its compatible Minecraft version and server type
• Make sure your server is running the correct edition — plugins need Paper/Spigot, mods need Forge/Fabric/NeoForge
• Mod loaders are not cross-compatible: Forge mods won't work on Fabric, and vice versa
• See our plugin installation guide or mod installation guide for more details

Connection Refused

If you can't connect and the error message just says "Connection Refused":

• Make sure your server is actually running — check the Console
• Restart both your game client and the server
• If using mods, ensure you have the same mods installed on your client as the server
• Verify you're using the correct IP address and port

Mismatched Mods or Versions

When connecting to a modded server and getting "mismatched" errors:

• Your client must have the exact same mods and versions as the server
• Download any missing mods or remove extra ones from both client and server
• Use the same launcher profile/instance that matches your server's modpack

Server Running Out of Memory

If your server is slow or crashing with out-of-memory errors:

• Check your resource usage in Activity
• Large modpacks need more RAM — you may need to upgrade your server plan
• Follow our Performance Guide to optimize your settings
• Consider preloading chunks to reduce real-time generation load

If none of these solutions work, join our Discord and we'll help you troubleshoot.