Exterior Lighting No Power Issue

[stormycs]

No voltage reading on both the right side taillights and lower amber marker light on rt side, which wiring diagram shows on same circuit. License plate light on same circuit, prior to the wire connecting to the nonworking lights, has power. Turn signal and brake lights work. Wiring schematic in my owner's manual shows that the wiring to the 7 way plug is in the ceiling on my 2002 23 ft. Safari. Any ideas of how I can best access the wiring? I'm assuming that the break is after the license plate light wiring.

[stormycs]

Ended up being a broken green wire and white wire 90% gone. No indication of why wires were damaged, but I suspect mice. No evidence of mice in that area, but have had mice issues last winter and before. Access by removing inner window trim & curtains, peeling back fabric from walls to access inner panels. Removed rivets to open panel. Access required cutting inner panel for better access. This was done at an RV dealership which works on Airstreams. Pretty pricy!