DIAGNOSIS The print resolution is set too low in your app, or you're scaling the label incorrectly. The printer's native resolution is 203 DPI.
FIX Change the label scaling to 100% and ensure DPI is set to 203. 1. In your shipping app's print settings or page setup, find the scaling option. 2. Set it to "Actual Size" or 100%, not "Fit to Page". 3. Look for a DPI or print quality setting—set it to 203 DPI. 4. Print a test label from the app's preview screen. The barcode should be sharp, not blurry or stretched.
IF THAT DIDN'T WORK You might be using a low-quality label brand that smudges easily. Test with a known brand like Avery or ULINE direct thermal labels to rule out material issues.
HEADS UP Never design your own label in a program like Word or Canva and try to print. Use your shipping app's native label template. Third-party templates often render barcodes at screen resolution (72 DPI), which will always fail USPS/FedEx scanners.