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# What to do if the sensor LED does not flash after battery installation

The contact sensor and motion sensor do not have a SYNC button. It broadcast itself once a battery is installed.

1. Remove the protection film outside the battery and reinstall the battery.

2. Read [this article](https://support.nooriolife.com/hc/en-us/articles/7358407408153) and check if the battery is installed correctly.

3. Replace a new battery if the old one is low power.

If it is still not working, feel free to contact us via support@nooriolife.com.