HELP!

I'm fairly new to this but I have seemed to find my waya round Corel fairly easy.

For some reason I can't figure this out though!!

I have basically made a circle and filled it in with a radial fountain fill. It looks great and then I save as a PDF.

The PDF shows it just fine but when I go to open it next in Corel it changes to a solid colour!! I then go to the fountain fill tool and all the settings are the same, totally correct. I cannot for the life of me figure this out.

PLEASE HELP (: