"Incompatible version" means your game and the server are on different Valheim versions, usually because a game update came out and the server doesn't have it yet. Game servers don't update themselves the way your Steam library does.
- Sign in to the control panel at panel.chicagoservers.co and open your Valheim server.
- Click Update now on the Steam update bar at the top of the page. The server stops, updates and starts again by itself.
Still incompatible? Make sure your own game is up to date in Steam (and on the same branch: not the public test). If you use mods, every player needs the same mod versions as the server: see How to install mods on your Valheim server.
Need help? Open a support ticket and we'll take a look.