Minecraft Server Won't Start - Troubleshooting
The five most common reasons a Minecraft server fails to start, and what to do about each on GameGrid.
Start With the Console
Open the Console tab and read the startup output from the top. The FIRST error is the cause; everything after it is fallout.
The full output is also in logs/latest.log, downloadable from the Files tab. That is the file to attach to a ticket.
If the server got far enough to crash rather than fail to launch, crash-reports/ in the Files tab has the detail.
EULA Not Accepted
Error: "You need to agree to the EULA in order to run the server. Go to eula.txt for more info."
On GameGrid the EULA is accepted for you. The platform writes eula=true into eula.txt every time the server starts, on all five server types.
That also means editing eula.txt to false through the file manager will not stick - it is set back on the next start. Accepting the EULA is a condition of running a Minecraft server, so the platform does not leave a server in a state where it silently refuses to boot.
If you see this error on a GameGrid server, it is not the EULA - read further up the console for the real failure, and open a ticket if nothing else explains it.
Wrong Java Version
Error: UnsupportedClassVersionError, or "A JNI error has occurred".
All five server types here run Minecraft 26.2, which requires Java 25, and the platform installs and selects it. There is no Java version to choose and nothing for you to install.
So on GameGrid this error is almost always a plugin or mod, not the server: something built against a newer Java than 25. Remove the .jar you added last and start again.
If it is the server itself and not an add-on, open a support ticket - that is ours to fix.
Port Already in Use
Error: "FAILED TO BIND TO PORT" or "Address already in use".
Your server's port is assigned by the platform, and the platform writes it into server.properties on every start, so this should not happen.
When it does, it usually means the previous process has not fully exited. Press Stop, wait for the status badge to read stopped, then Start.
If it persists, open a ticket with your Service ID from the Overview tab. Do not change server-port in the settings - it is shown read-only for this reason.
Missing or Corrupt Server Jar
Error: "Invalid or corrupt jarfile", "Unable to access jarfile", or on Forge and NeoForge a message naming user_jvm_args.txt and the loader's argument file.
Restarting does NOT re-download the server files. The start path launches what is already on disk.
Use "Reinstall Server Files" on the Overview tab under Quick Actions. It reinstalls the core game files and leaves your world, settings and mods alone.
"Verify / Repair Files" on the Admin tab is the lighter option: it checks the game files against the known-good manifest and repairs what is wrong.
If you selected your own jar in the Settings tab's "Server JAR File" dropdown and then deleted or replaced the file, set the dropdown back to a jar that exists.
A Plugin or Mod Crashes on Load
The add-on you installed last is the first suspect, and it is right most of the time.
Stop the server, open the Files tab, and move that .jar out of plugins/ or mods/. Start again.
If it still fails, move everything out into a folder like mods-disabled/ or plugins-disabled/ so nothing is lost, and start with the folder empty. A clean start proves the server itself is fine.
Add them back a few at a time, restarting between batches, until the failure returns.
Common causes: a mod built for a different loader, a build for a different Minecraft version, a missing library or dependency, or two mods patching the same code (which shows as a mixin error).
Remember which folder your server type uses: Paper loads plugins from plugins/; Fabric, Forge and NeoForge load mods from mods/; Vanilla loads neither.