You may want to troubleshoot some stuff.
1. Connect to the battery directly. If it turns on you have a working pump. If it doesn't turn on you may need to buy a new one.
2. Check all wiring. In my case the wiring to the panel was bad and the wiring to the batter non-existent. The previous owner must have little to no electrical experience. I put in heavy grade battery wire directly to the batter and rewired to the panel. Now the switch works and the backup direct power source work.
3. Sometimes you can change the float and it will work. In this case, it was internal and unlikely to be taken out. I certainly tried. Some can just be changed out directly.
4. Think of a back up pump. I'm keeping my eye out where I can wire in a back up pump. .
5. Make sure you have a manual and utility pump around. The last thing you want to deal with is a dead battery at sea and no way to get water out.