I have a simple sheet metal part that has a couple of flanges but when I select the Flatten Icon on my tool bar I get this error message. If I select the Flat-Pattern1 icon from the Feature Manager, Right Click and chose Unsuppress the part flatten and if I chose suppress again it folds back. What's up with the Flatten Icon on the tool bar?

Updated:

I found out why this is happening. I added two pem nuts as derived parts and then combined the bodies to form a siingle body. After I deleted the combine feature all is well. I guess I will have to live with a three body part.