This message means your sensor could not communicate with your reader or smartphone. Try scanning again.
• Hold your reader or smartphone against the sensor (for Apple phones, hold the top edge of the phone against the sensor; for Android phones, hold the back of the phone against the sensor)
• Remove thick clothing
• Move away from household appliances that emit electromagnetic waves (such as microwaves, Wi-Fi transmitters, baby monitors)
NOTE: The different phones have their NFC area in varying spots, the above is guidance in general, you can also try google searching the location sweetspot for your specific phone on google.