A jumper is almost never used with passive termination. 99.9% of all drives that use a jumper to enable or disable termination indeed have an active terminator.
It is possible that you don't have term power supplied on the chain. Even though the drive has a jumper to enable termination, it may require the power to come from the cable rather. The spec page you have doesn't have termination info, so you're probably left to your best guess. Some drives have the option to supply it to the chain. If any of your other drives have this ability, you probably should enable it.
I have a hunch termination isn't the only problem here though. The drive is a 16-bit drive, but putting the 68->50 pin connector limits it to 8-bit access. Assuming the Blizzard is the same as the CSPPC, get to the preboot menu and force the drive to 8-bit rather than Auto or 16-bit.
If nothing here helps, let me know. I'd be glad to try to work it out with you.
