Kathy -
Thanks for including the photo. My guess is that the solar power system is connected to the battery through the red wire near the bottom of the photo, so charging is taking place through that wire. On the other hand, the upper red wire is what brings power from the battery to the trailer. In your photo, look at the black carrying strap on the battery. Almost covered by this strap is a small black box in the upper red wire. This is the 30-amp main fuse in the battery line, and if it is blown, the battery cannot deliver any power to the trailer. Open up that little black box and pull out the fuse. If it is blown, go to a hardware store and buy a replacement - actually, you might want to buy several (a box of 5?) just to have spares.
Take a look at this picture in my TechStuff album.
https://www.trailmanorowners.com/for...pictureid=1873
An example of the little black box and the fuse is on the right. Your fuse may look slightly different, but it will have two flat blades. Buy a replacement fuse that looks like the one you remove. Again, it should be rated at 30 amps.
Bill