I had trouble getting one to work too; got it fixed eventualy after hours of fiddling. Pin 1 is marked on the cable; but not on the card. The red wire is on the simm holder side, if it's not already there.
Try removing the SCSI board and clean the contacts on both the Blizzard and the SCSI card. This eventually worked for me, probably just a dirty contact (though the effect was very different; my Amiga wouldn't boot, just a black screen)
