Is scanner connected to PC?
Unplug and plug in (try a different usb port, not monitor)
Is the the correct USB cable - no extensions or adaptors?
Check device manager, is scanner showing up as installed correctly?
Are drivers installed?
If windows 7 - is it 32 or 64 bit? is the correct driver installed?
(note: scanner model PS600-10 does not have 64 bit drivers)
Is the correct scanner installed in CDP software?
CDPCentral - tools > setup > password* > scanners tab > select scanner > save > close CDPCentral (also exit CDP Teller, close receiver, open receiver)
CDPManage - Document > select scanner > select correct scanner
*Call CDP for assistance if you do not know password.