Merry Fisher 645 leaking sun roof

[chris01]

Hi,  the sun roof of my MerryFisher 645 is leaking from the seal into the cockpit in the front left hand corner. I have tried to use marine mastic but it won't seal between the glass and the roof. The boat is only 3 years old so I find it hard to believe that the original seal has perished.
Has anyone else encountered this problem or have advice on how to get it fixed.

Thanks