Mento on 11 Sep, 2017 09:29 AM
it looks like, you have copied the keys to the smart card, but not deleted it from your local machine.
To solve this:
1. Make a backup of your .gnupg folder.
2. Delete your secret key using GPG Keychain. (Do NOT delete the public key!)
3. Plug in your smart card.
4. On the command-line run gpg --card-status.
Thank you for the walk-through. In fact, I did just that: deleted the entire key through the GPG Keychain (including the public key, to be on the safe side), then re-imported the public key only, and finally paired the imported public key with the card-based private key via "gpg --card-status". At which point I was again able to export the entire key (public + private keys) through GPG Keychain. Clearly the private key remains somewhere on the chain (even though not visible through GUI). Will try deleting private key only and will report back.