This message means that the burning drives are not recognizing the blank media. There are a few things to try and remedy this though the unit may need repaired.
First, try using all of the duplicator bays by burning to another drive bay. If all other drives burn fine then the one drive may need to be replaced.
2nd, try a different blank CD or using a different brand. The most common fault for this message is a bad blank disk.
3rd, It is OK per Microboards to open the unit and check for a loose drive cable. A loose cable can cause this error too.
Finally, try cleaning the drive bays by using compressed air to blow any dust out of the system.

If the error still continues then call Microboards tech support at 952 556 1639 to set up a repair.