How large is this piece of vinyl, where exactly is it, and how is it attached. As Andy said, it could be a cover for the roof-mounted air conditioning unit. It could also be a cover to deal with roof leaks that have not been repaired.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)