Cause:

1. Paper loaded upside down.
2. Not direct thermal labels.
3. Change to other USB port after installation.
4. USB cord broken.
5. Driver is not installing correctly.

Solution:

1. There is only one side for thermal paper to print, load the paper correctly, print side faced upside.

2. Heat transfer labels or thermal transfer labels are not available, use direct thermal labels. Use NELKO labels for best results.

3. Use the same USB port when installed. Or reinstall again.

4. Use another USB cable.

5. Uninstall the driver and reinstall.

For Windows, open the driver file, uninstall by steps then reinstall. Print Test Page to check if printer set up correctly.

For Mac, go to "System Settings"-"Printers & Scanners", delete printer, then add again.