Thermostat shows E0 and cannot connect to the Saunier Duval cloud or mobile app

Safety: No electrical work required.

• Check internet: Ensure your home internet connection is working on other devices.
• Verify account: Open the Saunier Duval app, log out, then log back in. Confirm the thermostat is listed under your devices.
• Re-link device: In the app, remove the thermostat (if present), then follow the add-device wizard to scan the QR code or enter the serial number.
• Check time: Make sure the thermostat date and time are correct; enable automatic time sync if available.

If E0 persists while internet is working, wait and try again later; if still unresolved, contact Saunier Duval support as it may be a server-side issue.