Why does the printer print first label correctly and then flash red light?

1. Label length longer than 300 mm/ 11.8 inch.

Solution: Use label of width less than 101 mm/ 4 in. and length less than 300 mm/ 11.8 in.

2. Select wrong label media type.

Solution: Go to "Settings"-"Device"-"Printers & Scanners"-"Label Printer"-"Manage"-"Printing preference", select "Labels With Gaps" on "Page Setup" tab.