Water seeks the travel path of least resistance, so the leak may, or may not be where you think it is.
Assuming that it is the awning rail though. There are usually "keeper" screws placed in the rail to prevent the awning fabric from sliding in the rail. I've seen some that were long enough to protrude through the rail and into the skin.
Also, Carefree used a lag screwed extrusion on their awnings at each end of the rail where the endcaps rest during storage. The lag screw openings are a very good leak point if not properly sealed.
After that I'd look at all other penetrations in the shell.
Best of luck,
"...the most confident critics are generally those who know the least about the matter criticised."
Ulysses S. Grant