How do you slave the disk? Try via USB. You don't need to import keys, as the key is already on the drive.
Run these commands while disk is on original machine and slaved to ensure you get the same results. Before running them, navigate to "C:\Program Files (x86)\PGP Corporation\PGP Desktop":
1. to check the disk number (numbers will be different for both cases - in original machine it will be probably "disk 0", when slaved it might have different number):
pgpwde --enum
2. to check the status of the disk:
pgpwde --disk-status --disk <number>
so, if the disk number is 0 the command will look like:
pgpwde --disk-status --disk 0
3. to check what users are assigned to it:
pgpwde --list-users --disk <number>
so, if the disk number is 0 the command will look like:
pgpwde --list-users --disk 0
4. You can also test if the passphrase you uses is accepted:
pgpwde --auth --disk <number> --passphrase <passphrase>
so, if the disk number is 0 and passphrase is Welcome!123 the command will look like:
pgpwde --auth --disk 0 --passphrase Welcome!123
Once you see "Request sent to Authenticate disk was successful" message after last command you entered, it means this is the passphrase you may decrypt the disk with.