Mac devices do not have a registry in which to store the identities of licensed software and accessories as Windows devices do, so software needs to be associated with a device name in order to run. If the device does not have a name, it cannot be associated with a software program, in this case Citrix/VLab, and so it does not run. Here's how to fix it:
Citrix Receiver for Mac should now run correctly.
More information and screen captures are available on the Citrix website..
If you are on a computer with a printer already set up, the Virtual Lab should allow you to print through to that directly. If you are on campus you can print to Library 101, Founders Hall 143 and BSS 316.