Thermostat displays E12 and cannot complete firmware update; device may reboot repeatedly.

Safety first: No high‑voltage work is required, but avoid removing the thermostat while an update is in progress.

• Step 1 – Ensure stable Wi‑Fi and power: Confirm the thermostat has a strong Wi‑Fi signal and that HVAC power is not cycling. Avoid turning breakers off during updates.
• Step 2 – Retry update: From the Geo app or thermostat menu, navigate to Settings > Software Update and retry the update. Allow sufficient time for download and installation.
• Step 3 – Reboot device: Remove the thermostat from the wall plate for 30 seconds, then reattach. After reboot, check if E12 clears and if the firmware version updated.
• Step 4 – Factory reset: If the error persists, perform a factory reset from the settings menu. Reconnect to Wi‑Fi and attempt the update again.
• Step 5 – Replace thermostat: If E12 remains after multiple attempts and resets, the internal flash memory may be defective. Replace the thermostat head unit.