Kessils are quite compact but powerful lights. This adds certain complexity to the repair.
The primary hope is that the LED array works and the problem is somewhere else on the main board.
Let’s take it apart and look inside:

Not looking too bad. There is a bit of dust here and there, but otherwise everything looks fairly clean.
Looking closer at the board explains why the condition is good:

You may be able to see that the board has a shiny hue to it. This is a protective silicone coating over the entire board. It prevents salt and humidity related oxidation that we are so used to seeing on other lights.

Let’s keep going. The goal is to take the board out and connect it to the bench power supply for testing:

Testing power input indicates a short to ground, but where is it?
Protective coating is great to protect against corrosion, but it makes it harder to diagnose and repair issues. It has to be removed prior to repair.
Let’s use some voltage injection we used with other lights to find it. That brings us to these diodes:

You can see that I had to remove protective coating to get to the diodes to test them.

Removing the first diode also removes the short! Aren’t we lucky today.
This diode appears to be there to protect the light from reverse polarity among other things.

Let’s grab a brand new diode, repeal and replace:

Now we just need to restore the protective coating and let it dry:

And the light is working again: