idp SMART Series User Manual page 91

 Bad USB cable.
Change the USB cable.
 The printing is operated with another printer driver.
Select the correct SMART-51 printer driver again.
 Wrong USB port setting of the printer driver.
Check the port setting of the printer driver and change the port setting.
 No ribbon in the printer or error occurred.
Install ribbon in the printer or resolve the error.
 Too long power or USB cable (more than 1.5M).
Use the cable provided with the printer.
 PC's USB port is down:
Reboot your PC.
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