How to Fix Red Light & Paper Recognition Failure via Printer Sensor Calibration?

June 11, 2026 23:34
Updated

Applicable Fault Symptoms:

If your 403B printer occurs abnormal paper calibration issues as below, please follow the steps below to complete sensor calibration:

Printer Status Light stays solid red
No response after pressing the FEED button
The printer fails to detect paper after loading media
Munbyn Print App shows "Out of Paper" alert even with paper loaded

Sensor Calibration Operation Steps:

1. Power off the printer completely, and make sure no paper is loaded inside the printer;

2. Press and hold the FEED button, keep holding it while powering on the printer;

3. Release the FEED button immediately once you hear a beep sound;

4. The printer will run automatically after you release the button;

5. When the printer stops running automatically, wait for 5 seconds;

6. Power restart the printer, then load paper and test the feeding function.

Further Support

If the paper feeding and printing failure still exists after finishing the above calibration steps, please contact our technical support team for professional assistance.