Troubleshooting / FAQ

A server won't start with UnsupportedClassVersionError (wrong Java version)

The pack needs a newer (or older) Java than the daemon's default. NexCraft tries to provision the right one automatically, but if it didn't:

1. Open the instance's Java Manager.
2. Pick the vendor (Adoptium / Azul Zulu) and the major version the pack needs (e.g. Java 17 for 1.18–1.20, Java 21+ for newer, Java 8 for very old packs).
3. Install a release and click Use, then start the server again.

The error message tells you the required class-file version, e.g. class file version 65.0 = Java 21, 69.0 = Java 25.

"This CurseForge modpack has no server pack"

That pack's author didn't publish a server pack file for the version you picked, so it can't be installed as a server. Try a different version of the pack, or use a pack that ships a server pack. (Modrinth packs use .mrpack and generally work.)

The server starts but players can't connect

• Check the port. NexCraft auto-assigns a free port from 25565 up; confirm server-port in Config Files → server.properties and that the port is forwarded/allowed by your firewall.
• For modpacks, make sure the server fully reached Running (not still Starting).

Status stays "Starting" forever

NexCraft holds the status at Starting until the server logs that it's ready (e.g. Done (…)! For help…). If it never flips:

• The server may have crashed during boot — check the console for errors.
• A safety timeout (15 min) will return it to a normal state; check the logs to see why it didn't come up.

I deleted a running instance and nothing happened (older behavior)

Deleting a running instance now force-stops it first, then deletes. If you're on an old build, stop the server before deleting.

The Minecraft page URL

The Minecraft builder lives at /#/minecraft (it was renamed from /#/market). Old /#/market links no longer resolve — use the Minecraft nav item.

How is this different from MCSManager?

NexCraft is a Minecraft-focused fork of MCSManager. The big additions are the modpack browser/installer, per-instance update and reset, auto-Java, and a streamlined Minecraft-only UI (no Docker-container instances, no Steam games). If you need Steam games, Docker-container instances, or commercial/multi-tenant hosting, use upstream MCSManager.

Where do I report a bug?

Open an issue on the NexCraft repository: https://github.com/Dpavlakis/NexCraft/issues