"No scsi device" buts its plugged in.

I keep getting that error message, i am trying to connect a iomega zip drive to my mpc2000xl. I have it on the correct number. I have a terminator. When i first plugged it in it worked, i looked through a few disks but when i went to save to it, i got the same error message again. It feels like this is a common problem. any suggestions?

thank you