Hi Alan,
I've read that others have seen that message to use Restore, and it puzzles me. If the disk from which you want to import has been made from the other B2 with the Export command, then it will be ready to Import. So if that is the case, then just ignore the message about Restore and proceed.
The only legitimate reason I can see for the B2 displaying that message about Restore would be that the folder organization on the import disk is not arranged as Artist\Album\tracks. On a disk that was created by the Export command, that folder structure would be contained under b2Export\music, but those top two folders are not required for the Import command to work.
For the disk you want to use for Import, are there any factors about it that are different than I just described? What software version are you currently running?