To factory reset a Zebra iMX320 you will need to link the printer to your pc and use the zebra printer tools to send the reset command to the printer

^XA^JUF^XZ^XA^JUN^XZ^XA^JUS^XZ

For full details please view this link https://km.zebra.com/kb/index?page=content&id=SO8407&actp=LIST