I fixed a similar problem in a friend's North Trail. In the trailers I've seen, including my BH 3010RE and my friend's NT, DC wiring is connected with wire nuts instead of crimped connections. In my friend's case, a wire had "escaped" from a wire nut, shutting off everything downstream. I found the culprit by removing a few switches from the wall and tracing the wiring which tends to be set up with a power supplying pair coming to a single point and branching off from there. I suggest starting at either the switch for the over-sink light or the light fixture itself (since those are probably easiest to get to) and tug on the wires from any wire nuts you find. There is usually plenty of slack in the wires so it shouldn't be hard to pull out few inches and examine any connectors.
Unfortunately, another possibility is in the wiring running under the floor from the distribution box to the kitchen area and covered by the, er, "underneath-the-trailer corrugated plastic cover stuff." I have found several problems in my own trailer in that wiring.
As with all problems electrical, there are other possibilities as well, but, based on your description, I would bet that you have an open connection somewhere. If that is what it is, I hope you find it in a place that is easy to find and get to.
Incidentally, I have gone through my own trailer and replaced as many wire-nutted connections as I could find with crimped connections.