Start there it is common for the connection to give trouble or for the wire running up the pulpit to rub thru.
You will find the wire coming out of one of the four pulpit tubes.
If you don’t have any luck with power at the connection then go hunting
Run a long negative wire up to the bulb from a good know negative such as a power connection at the mast
If you get the light working then you know it is in the negative leg.
Then try it the other way with a positive lead. Light then you know the break is in the positive leg.
Beneteau use negative busses off of a main wire. Check the negative wires at the panel. There will be a dedicated positive wire from the panel to a wego block then off to light fixture
Good luck