Maybe it's not leaking in thru the roof.
Maybe it's coming in else where. Like clearance lights, edge and or corner moldings, windows, doors, any place that has an intrusion cut thru the wall or roof are all potential areas for problems.
Leaks are very hard to locate because it can leak in one spot and show up in another. You may try to run water starting on the side it is leaking on starting at the bottom and working your way up the side. Check inside where you see the wetness until the last spot turns something up
It's important to find the source of the leak before you cover up any evidence of the leak. It is rare to need to seal the whole roof, if that is what you are doing.
As others have said, where the water is found inside may not be where the leak is.
Tom technical teacher Automotive service technician
You did not mention where the water is showing up. I have the same trailer. On mine I had a problem with where the awning attaches to the edge of the roof. The screws attaching the awning were not installed correctly toward the rear of the trailer over the outdoor kitchen and many screws were broken off. Water was intruding via the outdoor kitchen. By the way the screws are of poor quality. I put better ones in and sealed where the awning attaches. First trailer I had leaked at the forward clearance lights. Your trailer is not that old roof should be ok it is usually seams or places other parts attach.