Hold the Feed button down through 1 blink of the green light, 2 blinks of the green light, 3 blinks of the green light, and 4 blinks of the green light.
After the round of 4 blinks of the green light, stop holding the button. The light should turn red.
If done correctly, this should reset the printer. The light should be red and blinking during this reset period. Once it is finished with the reset, the light should become solid green. At this time, a printout of the settings can be obtained by holding down the Feed button for 1 blink of the green light.
NOTE: This does not change the network settings on the GK420d. Those must be reset separately using:https://help.valet-manager.com/a/solutions/articles/8000078905.