If your thermostat is still connected to Wi-Fi and you can see it in the Nest app or Home app, you can unlock and reset the PIN using the app:
Lock and unlock your Nest thermostat - Google Nest Help
If you can't control it using the app anymore, you'll need to reset it using a computer.
- Connect the Nest Thermostat display via USB to a computer.
- Verify that the Nest Thermostat mounts (appears as an attached drive icon).
- If the Nest drive will not mount: Restart the thermostat and the computer.
- If the Nest drive still won't mount: Connect another device to the cable to see if it appears as an installed device.
- If it doesn't appear, use a different cable/port/computer.
If the Nest drive is successfully showing up on your computer, can you see a technicalinfo.PLIST file? If you get this far let me know and I'll ask a community specialist to assist with next steps, as these can't be shared publicly in the community.
