Why can't I connect to my server?
Short answerCheck four things in this order: the server is running, you used the address from the panel, your game runs the same version as the server, and you are allowed in by the whitelist. The message Minecraft shows tells you which one it is.
Run these checks in order
Is the server running? Open your panel on Overview. If it says offline, start it and wait until the Console says it is done loading.
Is it the right address? Copy it again with the copy button on Overview and paste it, instead of typing it. One wrong letter gives "Unknown host".
Same version? "Outdated client" or "Outdated server" means your game and the server run different versions. Switch your game in the launcher, or change the server version in Settings.
Allowed in? "You are not whitelisted on this server" means the whitelist is on and you are not on it. Add yourself on the Players tab. A ban shows as a ban message and is removed there too.
Other messages
"Connection timed out" when the server is running: try again from another network, such as your phone as a hotspot. If that works, your own network or firewall blocks the connection.
"Mismatched mod channel list" or a list of missing mods: the server runs mods and your game does not have the same ones. Install the same pack and version.
Bedrock players on a crossplay server need the Bedrock port from the panel header, not only the address.
Everyone is disconnected at once
If several players drop at the same moment, check the service status page before you change anything on your server.
Questions people also ask
It worked yesterday and nothing changed.
Check the Console for a crash or a restart, and the version: the Minecraft launcher updates your game by itself, and then it no longer matches the server. Pick the server version in the launcher's installations.