A tamper error occurs when the panel is reading that the sensor's cover is not attached properly. To address the tamper error on your QS1231-840 motion detector, follow the instructions below.
1. Remove the sensor from the wall by pushing the bottom tab in and lifting the sensor off.
2. Note that the black lever is what reads the tamper.
3. To correctly close the sensor, line up the two holes on the sensor with the two tabs on the baseplate, and swing the bottom of the sensor onto the baseplate until it snaps into place.
You will need to clear the error from the panel memory by following these instructions: IQ Panel 2 - System Sensor Status.