Creo 4.0 Flat Pattern issues

Hello all, I am still relatively new to CREO. I am a college student and I had a class that dealt with modeling, but now I am using CREO for manufacturing/sheet metal use. I started out with a model then converted it to a sheet metal part. When I click on create flat pattern, I generate an error. The flange in my part will flatten, but the cone shape in the middle will not, no matter what I seem to try. Any help is greatly appreciated, thanks!