First try these steps:
Troubleshoot a Nest thermostat w5 code - Google Nest Help
If the issue persists after trying those steps, contact the Google Nest support team directly.
- Go to Contact Us - Google Nest Help
- Select an appropriate product or category, type a brief description of the issue, then click Next.
- Click Other, then click Next step.
- In the Resources section, click Next step.
- Choose to get a phone call, call or chat with the team, depending on availability in your country.
As it mentions in the article, have your thermostat’s serial number ready to give to the support agent before you call. To find your thermostat’s serial number, pull the display off the base and flip it over. The serial number is above the QR code on the back of the display. Mention to the agent you've already tried restarting the thermostat.
