Before you begin, make sure you’ve completed the basic troubleshooting steps described in this article.
1. Printer is not printing tickets
1.1 Media is not loaded properly
Ensure the media is installed correctly with the black mark facing down.
Load media, in this case it is fanfold paper and that the paper is inserted correctly between the yellow guides following these steps:
The black mark is face down:
The black mark needs to be aligned with the yellow sensor. You can move the yellow sensor manually from left to right to match the ticket black mark.
Place the ticket so that the black mark is towards you, (right before the opening) not towards the back of the machine.
You can find additional details on printing with Fanfold Media in the linked article.
1.2 Paper is not the correct type
The ZD420 and ZD421 require fanfold paper designed for Direct Thermal Printing.
Do not use roll paper with these models unless your setup specifically supports it.
Confirm your paper type using Zebra’s official guide: How to Test Labels for Direct Thermal Printing.
1.3 Printing is paused
If the printer’s pause symbol is lit or blinking, it means printing is currently paused.
Simply press the Pause button on the printer to resume printing.
1.4. Clear the print queue if printing is stuck
Open Services from the search bar and run it as administrator.
Right-click on Print Spooler and click Stop (leave the window open).
Then open File Explorer and go to:
C:\Windows\System32\spool\PRINTERS
Delete all the files inside that folder (this will clear the print queue).
Go back to the Services window, right-click on Print Spooler, and click Start.
2. My printer is printing double
2.1 Duplicate printer configuration
Ensure only one instance is active in Printnode to prevent duplicate jobs.
Make sure the printer is not added multiple times in the system (e.g. once via USB and once via network).
Go to Devices and Printers (Windows) and remove any duplicate entries.
3. Printer Not Detected in Windows
3.1 Printer Disappeared or Setup Changed
This can happen if:
The user deleted the printer.
The USB port was changed.
The driver was uninstalled or corrupted.
Solution:
Make sure that the printer is powered and USB cord connected to your computer or POS.
Change your powered printer to another USB port on your computer or POS.
Remove the printer from Windows entirely.
Reinstall using Zebra Setup Utilities or the official ZD420/ZD421 driver. More information in Install the Zebra ZD420/421 thermal printer article.
4. Printer is in Thermal Transfer Mode Instead of Direct Thermal Mode
Use Zebra Setup Utilities to change the print mode:
Open Zebra Setup Utilities > Select your printer > Click “Configure Printer Settings”.
Change the mode from Thermal Transfer to Direct Thermal.
If the setting doesn’t apply:
Your company’s firewall or security policies may be blocking changes.
Contact your IT support to temporarily allow Zebra Utilities to make device configuration changes.
5. Factory reset and Additional error messages
If none of the previous steps are working, you can then reset the printer to factory settings.
All error messages and symbols are listed on this page, along with the appropriate troubleshooting steps.