While I still use Norton's SpeedDisk to optimize older HDDs (HFS formatted, and never with HFS+ format), I have no other recent experience of its disk utilities, because I use Silverlining exclusively on 100+ drives, both SCSI and ATA.
That said, your experience suggests recognition, but no handshake, between Norton and the drive. If you do not value whatever came as files on the drive, your difficulty may be no more if you simply reformat the drive. 'Reformat' in the sense of re-establishing Apple's several (invisible to the user) logical partitions in addition to the 'volume' that appears on the desktop, one of which includes the SCSI driver for that invaluable 'handshake'.
Apple's utility HD SC Setup is (designedly) rather diffident about overwriting non-Apple drivers, so you may need a utility with a hairier chest to reformat your drive. The usual disk utilities, some commercial and some free, use Apple's partition scheme of necessity, but vary in their take-over capacities.
de
That said, your experience suggests recognition, but no handshake, between Norton and the drive. If you do not value whatever came as files on the drive, your difficulty may be no more if you simply reformat the drive. 'Reformat' in the sense of re-establishing Apple's several (invisible to the user) logical partitions in addition to the 'volume' that appears on the desktop, one of which includes the SCSI driver for that invaluable 'handshake'.
Apple's utility HD SC Setup is (designedly) rather diffident about overwriting non-Apple drivers, so you may need a utility with a hairier chest to reformat your drive. The usual disk utilities, some commercial and some free, use Apple's partition scheme of necessity, but vary in their take-over capacities.
de