Right Rear Tail Light Out

@RayJim
If you have a TAB 400, remove the bed cushions, remove (about 5 #2 square drive screws) the rearmost wood panel with the froli system "lily pads" and all the wiring to the tail lights and license plate light is exposed.
If you have a TAB 320 maybe some one else will jump in.
The lights are LED units.  If it is not a wiring issue, the entire light assembly will need to be replaced.  the individual LEDs are not replaceable.  Chances are very good that you have a separated wire.  The crimp-on wiring connections nuCamp uses are very susceptible to poor crimping technique.  Vibration from going down the road can cause them to pull apart enough to break the connection.

Here is some information.  Also search "Possible Parts Solution."
https://tab-rv.vanillacommunity.com/discussion/comment/125841#Comment_125841

First step in looking at something like this, is to determine what the actual issue is. All Stop Tail Turn (SST) lights have two elements in case of incandescent and both incadescant and LED have two hot wires and a ground.

In your case, what isn't working? Tail, brake or turn? Once you know what isn't working, then you 1st need to move way upstream to the pigtail on front of trailer and determine if you are getting correct signal (voltage) from tow vehicle. If you are it is from there back, if not it is in tow vehicle wiring.

Assuming expected behavior from tow vehicle, then and only then would you look at the SST assembly. First determine if correct inputs are making it there, if not it is in trailer wiring, if correct signal is getting to the TTL, then replacement would be next step.

You might see a pattern of divide and conquer to my outline here, it is a very successful method of electrical (and other) troubleshooting. The idea is to start away from the symptom and always be asking do I have the correct inputs and expected outputs at each step of the way. This saves replacing a SST for instance when really the issue is a bad pigtail for instance or even a fuse or wiring problem further upline in the TV.