Welcome to IRV2, ALO.
I would guess you have something coating the roof, maybe a "roof protectant" (wax or silicone) or something. Rubber-based lap sealants sometimes react that way to silicon-based substances, for instance. Try cleaning a small area with a wax removing cleaner such as ammonia and see if the sealant will stick after that.
You should probably call Dicor at (800) 837-2059 and ask for customer service or tech support.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL