You should first ensure that your Dexcom G6 sensor was correctly inserted: 

• Was the previous sensor session ended or is the system still trying to connect with a previous sensor?
• Is the transmitter’s serial number correctly entered into the receiver or smart device? Click here for how to pair your transmitter.
• Did you clean your sensor site with a topical antimicrobial solution (such as isopropyl alcohol) and the transmitter with a damp cloth or alcohol wipes?
• Did you remember to tuck the front tab on the narrow end of the transmitter into the transmitter holder before snapping in the wide end?
• Did you hear a click when snapping your transmitter into the sensor, and is the transmitter sitting flush in the sensor pod?

Watch this video on how to attach the transmitter:

During the warmup period, the Dexcom G6 CGM System may detect that your sensor is unable to retrieve glucose information once the session starts. At this time, the warmup period will end and your receiver or compatible smart device* will display the “Sensor Failed” screen. You will now need to replace the sensor.

*For a list of compatible devices, visit www.dexcom.com/compatibility