Texas Instruments TI-83 Plus User Manual page 46

This error indicates that the TI Connect™ or TI-GRAPH LINK™
software is unable to communicate with the handheld. The
problem is usually associated with the TI-GRAPH LINK cable and
its connection to the handheld or to the computer.
• Make sure the cable is firmly inserted in the handheld's link
port and the computer's serial or USB port.
• Verify that the correct cable type is selected in the software
link settings.
• Verify that the correct communications port (Com Port) is
selected in the software link settings. (This step does not apply
if you are using the USB port and TI Connect software.)
TI-83 Plus NoteFolio™ App Page 46