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 for 3 sec. 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"