this means the websocket connection was lost and reconnect failed to find the old circuit. this can happen if in a webfarm and host affinity is not supported/enabled, or the connection has closed for time period.
if it important to seamlessly reconnect, you can add server code to save state, and at app startup load the saved state and navigate to correct page. then change js to reconnect without the reload link.
note: modern browsers are getting aggressive about closing websockets when page is not in use. say its not the active window, or the browser is not the active application. Also check if the app pool is recycling.