To resolve the issue of your FreeStyle Libre 2 sensor not working after application, follow these steps:

1. Ensure Proper Application: Confirm that the sensor was applied correctly. It should be placed on a clean, dry area of skin, preferably on the back of your upper arm. If the sensor is dislodged, damaged, or incorrectly applied, it may not function as expected - learn more.

2. Check Activation Period: After applying a new sensor, it usually requires a warm-up period of at least one hour before it can start providing glucose readings. If this period has just elapsed, wait for around 15-30 minutes before trying to scan it again.

3. Restart Your Reader or App: Sometimes, connectivity issues can be resolved by turning your FreeStyle Libre reader or app off and back on again. This can help reset any temporary glitches - learn more.

4. Inspect for Error Messages: If the sensor continues to show “Sensor not working,” you may have a sensor error. Check for specific error messages, as indicated by your device. If the message suggests waiting, it may be a temporary issue - learn more.

5. Consider Environmental Factors: Make sure that the sensor is not exposed to external factors that could affect its performance, such as excessive moisture or movement. Ensure it is not submerged in water or under heavy clothing that might interfere with readings.

6. Replace the Sensor If Necessary: If you have followed all the above steps and the sensor still does not work, it may be faulty. In this case, you should consider applying a new sensor to see if that resolves the issue - learn more.

7. Contact Customer Support: If you continue to experience issues despite trying the above solutions, it is advisable to contact Abbott FreeStyle customer support or your healthcare provider for further assistance.

By following these steps, you should be able to diagnose and potentially resolve the problem with your FreeStyle Libre 2 sensor.