Label Printer Calibration Steps

If the Gk420 model or other label printer has a flashing red light. Follow the instructions below to recalibrate the printer.

Standard Calibration Procedure (2-Flash)

1.  Make sure labels are properly loaded and the top cover is closed.
2. Power On: Turn the printer on.
3. Hold Feed Button: With the light solid green, press and hold the Feed button.
4. Flash Count: Wait for the green status light to flash once, then twice, and release the button.
5. Calibration: The printer will feed a few labels to calibrate and stop

1. Open Printer Settings: On your computer, navigate to the Control Panel, select Devices and Printers, right-click your Zebra GK420d printer, and select Printing Preferences.
2. Access Tools: Go to the Tools tab (or Graphic Tools in some drivers).
3. Select Calibration: Inside the Tools tab, look for the "Action" or "Command" list. Select Calibrate media (or "Load factory defaults" if you want to reset and calibrate).
4. Send Command: Click the Send button. The printer will feed several blank labels to calibrate.
5. Finish: Wait for the status light to turn solid green

Alternative Manual Calibration (Feed Button) 

1. Ensure media is loaded and the printer is on.
2. Press and hold the Feed button until the green status light flashes once, then twice, then three times, up to seven times.
3. Release the button and allow it to finish calibrating

If the above steps didn't work you can do the following 

1.     Hold the Feed Button until the light flashes four times
2. Allow the printer to finish and then perform the 2 flash calibration mentioned at the top. 

Here is a Youtube link for the methods as well 

Physical Feed Button Reset 

https://www.youtube.com/watch?v=yPNNKgfCZn8&t=12

Using Tools/Preferences 

https://www.youtube.com/watch?v=PTAs1rvH1Dk&t=14