A four-step checklist that catches nearly every connection problem: status, address, version, and your own network.
Almost every "can't connect" comes down to one of four things: the server is not actually online, the address was typed by hand instead of copied, the game version does not match, or something on your side of the internet is in the way. Walk the checklist below in order; it catches nearly all of them.
Your server has to say Online before anyone can join. If it says Sleeping, press Wake up and give it a moment. If it says Offline, start it. Anything else, our guide My server status is Offline explains every status.

Use the copy button next to the server address on your server card and paste it into the game. Typos in hostnames and missing ports are the single most common cause. If the address shown includes a port (like :7699), the port is required; that is a rule of that particular game, not something we control.

Your game and your server usually need to run the same version. If your game updated recently and the server did not (or the other way around), joining fails, often with a misleading error. Check the version setting in your server's settings and pick the one that matches what you are playing, or update your game.

Try joining from a phone hotspot, turn off any VPN, and make sure a firewall is not blocking the game. If a friend can join and you cannot (or the reverse), the server is fine and the difference is on the player's side.
Some games have their own joining rules: crossplay between platforms may need to be enabled on the server first, console players sometimes need an extra step to reach any third-party server, and a few games list servers in an in-game browser that can take a few minutes to update. Check your game's guides under game support for the specifics.
First glance at status.haptic.gg to rule out a rare platform issue on our side. Then message us on Discord with your server name, the game you are connecting from (and platform), and a screenshot of the exact error. That is everything we need to dig in, and we are quick.