If its the "You are offline, log in again". Try leaving the game for 30 mins or an hour. I left the game when it happened to me alot and it worked after some time. I this doesnt work, redownload miniclient (If you have it) or contact some about it, though I dont know if they answer.

Hey

Connection with our servers and normal usage of browser differ.
You may experience great video quality, however, different results with the game.

I'd advise clearing your cookies/cache and restarting your browser. If you're still experiencing connection issues. Flush your DNS

If you have any questions, feel free to message me.