This generally occurs when the imager is not being detected by the Ann Arbor Digital Devices Software.
Is the A2D2 Software is up to date? If not try updating the latest version compatible with your system.
Can you access the imager through File Explorer or "My Computer"? This will help determine if the issue is hardware or software based.
Run though the troubleshooting guide located below:
Imager Connection Error Sheet
If that the troubleshooting pdf doesn't work then inspect the wires for any damage, kinks or cuts that could be preventing communication.
(If the issue is occuring on a model 128s check the power adapter, the black box, for any loose connections or rattling noises)
Should damaged wires be the cause you may send an email to the support department for a repair quote.
This section is for A2D2 Software Error Codes and general troubelshooting. (It will be continually updated)