Unable to authenticate with Saunier Duval account (France / MiGO app)

[tomahoax]

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I'm unable to authenticate with my Saunier Duval account from the MiGO app using the myPyllant integration in Home Assistant.

Despite selecting:

• Country: France
• Brand: Saunier Duval
• Correct login credentials (confirmed working in the MiGO mobile app)

I always receive the following error:

Authentication error. Please check your username, password, country and brand.

What I tried

• Confirmed credentials in the MiGO app (login successful)
• Created a new account, reset password, and re-registered my boiler
• Selected France and Saunier Duval during setup
• Tried both in UI and after full Home Assistant reboot
• Turned on debug logging (see below)

Debug logs

mypyllant.api Got login url ...
mypyllant.http_client Sending POST to /login-actions/authenticate
mypyllant.http_client Got response ...
mypyllant.api Got login response headers ...

There is no explicit error from the API endpoint, but the Home Assistant integration still displays an authentication error.

My setup

• Boiler: Saunier Duval Isotwin Condens 25-A
• App used: MiGO (France)
• Home Assistant: Yellow, Core 2025.x
• myPyllant: latest version via HACS (v0.9.2)
• myPyllant config: via UI
• Debug mode enabled in configuration.yaml

Request Could you please confirm whether French Saunier Duval MiGO accounts are currently supported? It seems that the backend might be rejecting OAuth flows for this region/brand combination.

I'm happy to run tests or provide more logs if needed.

Thanks for the great integration!