The OpenPGP key was created with service of my email provider. It was my
business account. Then I exported private key from service to my Mac and
imported to GPG Keychain. Everything had been working perfectly. Then I
cancelled my business account. The passphrase has been working for some
time (more than year) - I could read downloaded to Apple Mail encrypted
letters without problem. But after some time it has been ended. Now I
can’t read my old encrypted letter and decrypt files which were
encrypted with this passphrase.
I have also similar situation with my private account with the same
provider. In the beginning I have done the same procedures: create,
export, import. I still use my private account but now I have the
following situation: I can still use this private key with Apple Mail
but it does not work with decrypted files.