If the sensor has come apart you will likely see a Tamper status reported on your Frontpoint App/website and Control Panel. The sensor is designed to open and should be able to be put back together without any issues. Hook together the top end of the sensor first, then snap in the bottom end. Ensure the sensor has closed completely and check on your Frontpoint App/website or Control Panel for the tamper status to clear. If your sensor is still showing as Tampered, please contact Customer Support.