Why is Spiral Knights not launching?
If it's the icon on the taskbar, then it could just be that the game window isn't being switched to. If you can, open task manage (ctrl+shift+esc) and click spiral knights on the applications tab. There should be a 'switch to' button. That is, if it's actually working like that.
How to fix Spiral Knights?
Rebooting Modem or Router
This can usually be resolved by rebooting the device. If the device does not have a power button then unplug it and wait about 20 seconds before plugging it back in again. Once the device has finished it's power on sequence try playing Spiral Knights.
Why is Spiral Knights so laggy?
When your Spiral Knights connection is laggy, it's usually due to a poor connection between 2 or more points. For example, your computer may be the Sender, and the Spiral Knights server may be your Target, but there could be other mystery hops along the way causing issues.