Hi @grahamc. Those were excellent troubleshooting steps to try. The main reason a Glass Break Sensor will go into a tampered state is because the tamper switch is not pressed down correctly when the sensor is closed. I would recommend double-checking that you have the lock symbol aligned with the line. If you have tried this step and are still having the same concern, give our support team a call at one of the numbers available here for further assistance. If you are outside of the US, please visit here to see how to contact support.