Most longer trailers, 26'+, have the awning rail butted together, due to the needed length. As stated, the leak is probably at the joint. Ours did, and even the factory failed to seal it up a second time!! I used a rubber cement (for the roof) and, after cleaning the sloppy job of sealing previously done, applied a few coatings of the rubber roof cement.
So far, after 3 trips, a couple of rains, no leakage. The glue is pretty liquid, and flowed into the joint much better than just a covering of silicone or sealant.
Also, the butt joint was uneven, one section slightly higher than the other. The sealant gob, blocked the channel somewhat, and the leak would continue for quite a while till drained completely. Leaked right over a side window. At least it wasn't over the door!!!