Hi folks, 

@Huib, uh-oh! I'm sorry to hear that you can't add your second Nest Protect. Follow these: 

1. Quit and restart the Nest app or Google Home app.
2. Make sure Bluetooth is on. Turn Bluetooth off, then back on to refresh the connection.
3. Restart the phone or tablet.
4. Make sure the assisting device is awake and within pairing distance (maximum of 2 to 3 meters).
5. Restart the assisting product.
6. Move the joining device and mobile device or tablet closer to the router or the router closer to the assisting product.
7. Put the mobile device or tablet on Airplane mode, then turn on Bluetooth and Wi-Fi.
8. Try a different mobile device or tablet.
9. Restart the network equipment (router, extender, or modem).
10. Reset the joining device to defaults.
11. Try to manually enter the entry key instead of scanning.
12. Test with a mobile hotspot.
13. Create a new home structure and try to pair the problematic Nest device.
    • If the Nest device pairs, the customer can use the new home and delete the old one. Ask them to reset any devices in the old home, then add them to the new home.
    • If the customer wants to keep the old home, have them remove all devices from the home > reset the account connection > connect all devices using the same network (Settings > Network), then pair the Nest devices in the app.

Let us know how it goes.

Thanks for your help, @code_. 

Best,

Zoe