Nest won’t power on

[Russgo]

I’ve used my best for 3 years with no problem and now it won’t work. I’ve replaced the battery. Cleaned terminals. It won’t power on. When connected it makes a fizzing sound. 

[zoeuvre]

Hi Russgo, 

Yikes! I'm sorry to hear that your Nest Thermostat won't turn on though you've replaced its batteries already. Let's see what's going on. A few questions:

1. Are you located in North America or Europe?
2. When did the issue first occur?
3. Are the power breakers on, and do you receive power to your home?
4. Is the thermostat's display seated properly?
5. Are all the wires of your thermostat seated firmly in its terminals (with no loose or exposed wires)?
6. Did you change the batteries with the recommened AAA 1.5 V alkaline batteries, such as Energizer AAA 1.5 V Alkaline Battery from Energizer? 

I'll look forward to your response. 

Best,

Zoe