Probably your sensor is not well installed or the sensor is defective. You can follow the points below to troubleshoot.

1. Manually move the two sensor parts close (less than 1/4 inch) or apart, to check whether the Meross app updates the right status.

2. Make sure the sensor cables are well connected to the smart garage door opener. If you disconnect the sensor wire, the device is indoor open status. Please try to short the two pins in the red connector（if the door shows closed in-app, then the device is right. If not, please contact us for device replacement (a sensor may work, but the device has a defect).

If both points do not help and your MSG100 is still under the 1-year warranty, please email the below things to support@meross.com, we will send you a new sensor.

1. Amazon order ID of MSG100.

2. A short video showing the sensor is defective.

3. An address for the sensor shipment.