Hi @tomplessers ,
This is the right thread for discussing any issues with Aqara FP1 sensor.
When pairing to HE, can you monitor the Zigbee logs ( Settings -> Zigbee Details -> Zigbee Logging) in a browser tab?
Do you see any unknown device there?
Also, I suppose you have already tried rebooting the HE hub first? I have had similar strange issues (with other Zigbee devices) resolved when pairing right after the hub was rebooted.
