Work through this in order; most cases end at step 3.
- Is the server running? Panel → console shows it running and, for Minecraft,
Done (x.xs)!. A server that is starting or offline refuses connections. - Right address and port? Copy from the Network tab, no spaces, port after a colon (
node1.penguhost.com:4123). "Unknown host" = typo in the name; "Connection refused" = wrong port or server down; "Timed out" = something in between (firewall, provider). - Right version? Minecraft shows "Outdated server/client" or a red "Incompatible" in the list. Steam games show version mismatch after updates. Restart the server.
- Whitelist or password? "You are not white-listed" is not a network problem. Check whitelist / server password.
- Only one player affected? Then it is their side: home firewall, VPN, school/work network blocking game ports, an ISP hiccup. Test from a phone hotspot. If that works, it is their network.
- Everyone affected, server running fine? Check our status page. If it is green, open a ticket with the exact error text and time.
Kowalski can run the first four checks for you: "why can't my friends join?".