E17 displayed and thermostat cannot connect to Atlantic cloud services while Wi‑Fi appears connected.

Safety first: No electrical work is required for this fault, but avoid repeated hard resets during firmware updates.

• Step 1 – Check internet: Confirm that other devices on the same network can access the internet. Restart the router if needed.
• Step 2 – Verify time and date: Ensure the thermostat’s time and date are correct, either via automatic sync or manual setting. Incorrect time can cause TLS certificate failures.
• Step 3 – Update firmware: If possible, trigger a firmware update from the Atlantic app or thermostat menu. Keep the device powered and connected until the update completes.
• Step 4 – Router settings: Disable any firewall rules or parental controls that might block outbound connections on ports 80 and 443 for the thermostat. Avoid using captive portals or guest networks that require web login.
• Step 5 – Try mobile hotspot: Temporarily connect the thermostat to a mobile phone hotspot. If E17 clears, the issue is with the home router or ISP configuration.
• Step 6 – Wait for service restoration: If Atlantic has a known cloud outage, E17 will clear automatically once service is restored.