Look at the browser console (in the client you are using) and check if you have any CORS related errors. For web clients the CORS headers need to be set, or the browser won't allow the connections.

There is also the change that the web client used for testing is being served using a secure connection (https) and the browser won't let it use insecure websocket connections (ws). In that case you should upgrade to wss.

(For desktop or mobile clients any of the above should not be a problem. However for those clients you should make sure the device is also connected to your tailnet).