Hi, I just bought a second hand nest E thermostat. The thermostat didn't come on when I plugged it in, but I pulled the front off the base and plugged in via USB. This worked and charged the unit, and allowed me to pair with my phone.
Then came to pairing the heat link and it didn't work. Tried putting thermostat back on base, this didn't work.
Thanks for reaching out. Here are some steps you can try:
1. Turn off all the devices in the room that are using Wifi or Bluetooth.
2. Reset the thermostat by pressing it quickly 2 times and then press and hold the display for 5 seconds.
3. Reset the Heat Link by pressing its button 1 time to wake it up and then press and hold for 15 seconds.
4. Power cycle your phone.
5. Open the Nest app and create a new home structure.
6. Enable airplane mode on your device and then enable your Bluetooth and Wifi.
7. Add the thermostat to your new home ( you can also try to add it without scanning the QR code ).
Let me know how it goes.