It's probably just a reverse polarity problem. If they are wired backwards, they won’t work — but it won’t harm them. Boat wiring isn’t very well standardized so you can’t really rely on the color coding. Try reversing the leads.
If you’re using wiring from previous lights, refer to ‘Is your old wiring adequate?’
Also check your connectors. We have seen crimp-on connectors that were crimped mostly on the insulation with just the slightest bit of wire touching.