Then launch the above Request and create the CertificateSigningRequest.certSigningRequest file. Just to be sure that you aren't accidentally skewing your Request with some random selection, go to your Login Items and select the Apple Worldwide Developer item. The Keychain Access > Certificate Assistant > Request a Certificate from a Certificate Authority is actually contextually aware of what you currently have selected when you launch it. If you are still having issues, revoke your current cert and start fresh. Spent quite a bit of time on this today, issues from not being able to create a SigningRequest to generating a distribution cert and not having it attached to my private key in Ke圜hain Access. If you are creating your own Distribution cert, not using someone else's then this could help.