Thanks for all the help. I eventually uninstalled and reinstalled FreeCad and now it seems to be OK though I haven't printed it yet. I don't know what I was doing wrong but I believe it may be OK now. Thanks again.

I have designed a simple part. However when I try to export it as an STL file many of the features are missing. I have tried highlighting all the components in the model as well as individual components and cannot figure out what I am doing wrong. It did work one time where I only highlighted one fe...