Hi Casey.
You are correct that it is pointless to try to add this drive in NBU if the operating systems can't see the drive.
And, since 2 different media servers can't see the drive, it suggests some other common point of failure. If you are convinced that the drive is properly connected, a switch or bridge could be a likely culprit. There could be a hung SCSI reservation on that type of device that is causing the problem. The best thing to do would be to power down all devices and servers and reboot "backwards in the chain." That is, boot the devices in the following order, giving each device a few minutes to properly initialize.
Library
Switches / Bridges
Media Servers
If that still doesn't work, contact STK and find out how to install their Web interface into the library. There should be one available. The significance of this is that rather than seeing the drive directly at the robot, you introduce the same elements (O/S, switches, etc.) upon which NBU depends.
If you are unable to see the drive via the Web interface, you can force STK to take more ownership. You can say, "Hey guys, it's your drive and I'm trying to use your utility, what's up?"
Let us know how things go.
Mojo