Wiring question.

I was able to check the truck terminals.
1 ground
2
3 battery
4 battery
5 left brakes
6 right brakes
7

Looks almost good with the exception of 3 being battery. 3 should be taillights. Were possibly the lights or daytime running lights on when you took the readings?
Although even if you do have battery on both 3 and 4 it's not the end of the world. Basically you're trailer running lights will be on any time the umbilical is plugged in which is not necessarily a bad thing.

Take a picture of the battery wiring and disconnect the trailer battery. Only disconnect one side of the battery. It's not necessary to disconnect both sides.

Pull all the wire nuts and separate the wires except the large nut for the white wires and the two large red wires. You now have two bunches of wires. One bunch is the trailer lights. The other bunch is the end of the trailer umbilical.

Test to find the bundle of umbilical wires.
Slide the black probe up into the large wire nut for the white wires, this is your ground. Write down what each wire does based on what the helper is doing in the truck. If you get no readings hitch up the trailer and try again. If you now get readings you have a ground problem. Just leave it hitched for now if that's the case and continue testing.

Check the voltage on all the single wires (green, white and yellow) I'm betting they all read 0 because they (or at least the green) was fed by the trailer battery.

(color) Right turn or brake
(Color) Left turn or brake
(Color) Tail
(Color) Battery charge
(Color) Brakes
Single green
Single white
Single yellow.

Troubleshooting or additional testing:
If you're unsure of your trucks wiring or the umbilical wiring do the following.

Unplug the umbilical and unhitch the trailer.
Reconnect the trailer battery.
Take a voltage reading from single green to single white (red probe on green wire and black probe on white wire).
If you get 12v positive you know green is trailer battery power. If no power try measuring from single green to bundle of whites.

If the green wire is 12v + you can use it to connect to the different colored wires and identify what each color wire does. On the trailer side of the bundle hook the single green to a wire and go see what lights are on. Make sure to write it down.
Remember a taillight will always have the side markers on at the same time.

If the lights all work you probably have a problem with the umbilical or the ground to the truck.

I did actually have my lights turned to Auto when I checked those terminals, I had forgotten to turn them to On because I never use the On setting. One strange thing about this is I hooked the trailer umbilical back up after checking the truck terminals and the left trailer blinker and left trailer brake light started working. I also do not have a battery on the trailer at all yet. I thought the trailer lights always took power from the truck. I do have a deep cycle i can use on it temporarily. I planned on buying a new battery for the trailer since it didn't come with one and the one I do have is quite old, not sure how much life is left in it.

You are correct that the trailer lights are supposed to take power from the truck. But the puzzling thing is that single green wire not even in the junction box should in theory not play any part in the lights.

Turn signal and brake light use the same filament in the bulb. Could it be as simple as a burned out bulb on the right taillight? If you don't have a spare bulb you could always swap the bulbs side to side.

I had hooked the white to the whites and the green to the greens and the front marker lights started to work. I haven't replaced any of the bulbs yet but I checked them for broken filaments. That was before the left side started working. I'll try a new bulb on the right side.

My Lance uses green and white for the running lights. If this is a front bedroom, those wires probably go up under the front cap then through the roof to the back. Stop/turn probably down thru the floor and thru the underbelly to the back.

So the test you did at the truck connector with the multimeter.,...you need to repeat that in the trailer. Find all 7 lines that come thru the umbilical and test them to see which is which, it seems like there is no reliable color standard. Once you figure out what's coming in, then you can figure out where it goes. If you pull the back lights you should be able to see what color they used for right and left stop/turn.

I separated all the wires except for the large whites and the large reds. With the umbilical plugged into the truck, i got 12v at one of the green wires, i got brake and right blinker at one of the browns, and brake and left blinker at one of the greens. I also opened up the tail lights to check wire colors. There is a brown wire on the right side. Should I hook everything back up and check for power on that right side? (Everything is working on the left side.)

Wow so you have 12v+ on one green wire and brake and left blinker on another green. Are either of those mentioned green wires the single

I would take the green wire that has 12v power and connect it to the wires on the trailer side of the box and then go look at the back of the trailer and see what colors go to which lights. Then hook everything up accordingly.
Did you get any power at all through the small red wire off the umbilical?

I keep thinking about this but I forgot to mention it. There might be a short in your umbilical. between the plug and the junction box. Is there any damage or repairs you can see in the cord? Has the plug been replaced at some point? Or is it still the factory molded plug? If the cord is damaged you'll have to either carefully slice it open and repair. Or just replace the cord and be sure it's right.This is the one I used to replace my cord and I'm very happy with it.
Link

Tie some strong cord to the wires in the junction box before you pull them all out of the trailer. Then you can hopefully use that same cord to pull the new wires into the box.

Edit: I just realized you gave us some information that we all missed. When you plugged the umbilical in a second time you had more lights working. I've been in your shoes before and you have a worn out socket on the truck or worn out umbilical plug on the trailer. So unfortunately any umbilical tests inside the trailer are suspect because you can't be sure you actually have a good connection at the truck end.

I think you nailed it with your last sentence. I hooked everything back up and then cleaned the terminals on the umbilical. They all looked questionable but one in particular looked rusty. I cleaned them all and all the lights work now. Keeping my fingers crossed that they will keep working. If not I will run a new umbilical as you suggested. Thank you guys for all of your help.