Why won't the lights on my trailer work?

I have a 5x8 CARRY on utility trailer and Im having a little trouble with the lights. If you were looking from the backside of the trailer, it would be the right side. The running light isn't working but the blinker and the brake lights work. The orange reflector on the side that is always on isn't working either. I check by the plug and there were no loose connections. Can anyone help me trouble shoot this or give suggestions? Thanks