E9 displayed; thermostat cannot complete firmware update or shows error during update via Ally app.

Safety first: No mains work is required for battery devices, but do not open the sealed electronics.

Steps:

• Ensure strong signal: Move the Ally Gateway closer to the thermostat or reduce obstacles to improve Zigbee signal strength.
• Replace batteries: Install new alkaline batteries in the Ally radiator thermostat before retrying the update.
• Reboot gateway: Power cycle the Danfoss Ally Gateway and wait until it is fully online before starting the update again.
• Retry update: Use the Ally app to restart the firmware update. Do not operate the thermostat or remove batteries during the process.
• If E9 persists: Remove the device from the Ally system, factory reset it, re‑add it, and attempt the update once more. If it still fails, the device’s memory or firmware controller may be defective and the thermostat should be replaced.