I looked online and couldn't find away. I know if there is away to reset it its a certain button combo. I would suggest contacting @AnkerSupport at email@example.com. Their response time is limited since we are going into a weekend and many of the staff are off for Chinese New Year.
You might also give them your serial number, when you purchased/order number, what's wrong the device, and what troubleshooting steps you have tried. This will speed up your request.