If a removable drive such as a USB drive is encrypted to a PGP key rather than to a username / password, it cannot be accessed by Encryption Desktop Drive Encryption.
The user is prompted for the passphrase of the PGP private key but even though the correct passphrase is entered, it is not accepted and the drive cannot be accessed:
This issue applies only when trying to authenticate to the drive using the following releases:
This issue was first present in Encryption Desktop 10.4 and was resolved in Encryption Desktop 10.4.1 HF1. Please contact Technical Support in order to obtain this hotfix.