"I tested a Zip Plus drive on our StarMax without difficulties. So there is no inherent incompatibility between StarMax systems and the Zip Plus drive. The Zip Plus drive does have automatic termination. With your system perhaps it is not providing sufficient termination. To test this, try daisy chaining the Zip Plus drive with another SCSI device. You should put the Zip Plus first in the chain and use an external terminator on the other SCSI device. If this works then the problem was termination. If you want to use the Zip Plus as the only external SCSI device you may need to get a 25 pin SCSI external terminator for it. If you still have a problem, try the Zip Plus as the only external SCSI device. You should start the StarMax off either the OS 8 system CD or the StarMax system CD. You need to make sure that the Zip Plus drive has a Zip cartridge in it while the StarMax boots up. This will make the system load the Iomega Driver from the Zip cartridge. In this case, if the Zip Plus drive mounts the cartridge, the problem lies in the system software on the hard drive. A clean system install of OS 8 may solve the problem."
Carrie found that termination problems were indeed the likely cause of the symptoms (placing the Zip first on the SCSI chain, rather than last, seemed to help). Bill Bowman reported a similar situation.