When the printer doesn't accept a label was printed correctly, it will attempt to re-print it.

Try the following steps to re-run "Automatic label identification" so printer can determine the label size.

①Turn power switch off . This clears any pending print jobs.  

②Turn power switch back on. Insert label from the back of the printer. Label will be automatically caught by the printer.

③Press and hold the Feed Button. After the blue light flashes 2 times, then release. Printer will move the label back and forth to determine the gap size and other properties of your label.

④When the label is positioned at the tear off point; continue to print. It should resume printing.

Check the video "Automatic label identification"