In the build options for the Windows phone 8 app, I can't select a publisher ID / signing key. Even when I add a new key, the dropdown is emtpy and says "No key selected". How can I resolve this?
What version of Phonegap are you using?
If you are using cli-6.0.0 or lower, you'll sign your Winphone app with just a Publisher ID string. If you're using cli-6.1.0 or greater, you'll sign your Windows app with a pfx signing key. I'm guessing you've added a Publisher ID, but are using cli-6.1.0 or greater -- you need to upload a Windows pfx key.
Some more info:
Thanks! I was on 6.5.0, now changing to 6.0.0 until I have time to get a pfx signing key.