I don't know about that specific version of switch, but I suspect either the cables aren't working properly or the valve isn't. Does the livewell have a drain hole in the bottom? Have you tried just plugging it? Otherwise, look on the transom. You probably have a fill (it will have that bubble screen on it), as well as the drain. You can plug the drain hole from the outside. Use a garden hose to fill the livewell and see where it drains out of the transom -- that's your drain hole.
Next time you're on the water, try to fill the livewell. If it won't fill, you've plugged a hole that allows water to fill it.
You MUST be careful. If you run the fill and it overflows, that water is in your bilge area. So, make sure you don't leave the fill pump on. Also, make sure to flip the bilge pump on occasionally just to make sure the livewell isn't cracked and leaking.
The best fix would be to find the actual valve and see if it's working correctly.