Can't add Honeywell T6 (Code 400)

Hardware
1

I’m trying to integrate my Honeywell T6 Thermostat with Home Assistant but keep getting the following error:

{"code":400,"message":"The redirect URL provided does not match the redirect URL registered for the app."}

I Registered the callback URL as http://homeassistant.local:8123/auth/external/callback and https://homeassistant.local:8123/auth/external/callback (using HTTPS).

  • Tried using my local IP address and DuckDNS URL (https://<mydomain>.duckdns.org:8443/auth/external/callback).

I’m unable to get the callback URL working properly. Any guidance on resolving this or correcting the URL setup?