Did you check your endcaps? If one comes loose, the whole system shuts down. If you turn the lights on, and it flickers and then shuts off, one of the endcaps is probably ruined and you'll have to replace it. Make sure that you don't have the ballast sitting on top of the tank because the humidity and the salt creep will fry it, that's why they give you so much wiring lol. Check your wiring, something may have disconnected, and like the endcaps, if one is out, it won't work.
If the wires and end cap fiddling doesn't pan out, call Icecap, they're usually pretty good with customer relations in the way of replacing malfunctioning ballasts.
Hope this helps