I'm using kleopatra to manage my certificates and I've exported both my private and public keys from my current machine. Copied them over to a freshly installed Kubuntu Virtual machine. Setup a KMail identity and attempted to add the signature and encryption keys.

Added the key for signature but it won't allow me to add the Encryption key. When I select it it's marked with a red X.

what am I doing wrong?

Question, are these separate keys, or subkeys? Also, did you set trust to ultimate for the keys that you imported?

I've created the key pair using Kleopatra. I have a private and a public key. There are no subkeys involved.

I didn't check the trust setting. Taking a look at it now.

Changed the trusting to ultimate. It works now. Thank you.