I have a map and an inset map. The content of the inset map's data frame is a direct copy and paste of the content of the main map. Both layers have (in order from bottom to top) a base map layer, a polygon feature class with 60% transparency, and a point feature class. When I export the map to any file format (pdf, png, bmp, jpeg), the transparency of the polygon feature class is preserved on the main map but on the inset map the polygon feature class is rendered opaque (0% transparency).
Why aren't both being rendered transparent?