Still having wiring issues on a Sunset Creek

Ok guys/gals...Ive been having an issue when I hook up my travel trailer to my truck. The problem is that my running lights will not work when I turn on my lights. My blinkers work, hazards work, and my brake lights work but the running lights won't. So me and my neighbor tried to pin point the area the problem could be in. When I checked the 7 pin on the truck, it shows that it has power (12volts). When I hook up the trailer I would go under it to the junction box and start testing the wires. it is only about 5 foot from the truck to the junction box. Well there's no power. So we unhooked the plug from the truck, replaced it and still nothing. so we unhooked the plug again and we took the green wire (which is the running lights wire) and put it on the battery on the trailer.. guess what....the lights came on. Hooked the plug back up and nothing. Unhooked it again and put the green wire back on the battery and BINGO we got some lights. But when I hook it all back up it still want work. Well we Ohmed the wire to see if there was a break in the wire and it checked perfect....So now Imt lost. I was thinking about putting a toggle switch from the battery to the running lights so they will have work when I turn on the toggle switch...Does anyone have any other suggestions?