Issue with Publisher and Package Family Name when uploading app to MS Store

Question

After associating my app with the MS Store, the Publisher and Package Family Name fields in my Package tab are greyed out in the Package.appxmanifest file. Even though the information in these fields is correct, I can never get the correct values to "un-grey" when I try to "Choose a Certificate". As a result, when I upload the app to the Store, I get two error messages indicating that these fields have incorrect values. How can I create/re-use a Certificate that will work with the app upload? I have tried multiple options for Certificates.