Hi all, have had the pub/sub Nest integration working for years, but recently got a new Gen4 thermostat and couldn't get back to the individual device authorization page, so I removed the entire thing and re-added it. Bad idea! I can get all the way through the flow and authorize the new device, but the final step fails when redirecting back to my HA instance. I set the permissions, choose my account, acknowledge that Google hasn't verified this app, and grant home-assistant.io access to my account, then the final step is "Link account to Home Assistant?"
When proceeding from that step, it just drops me at a white page with 400: Bad Request.
My "my" integration has the correct URL for its alias, the redirect is happening to my actual server, but the actual /auth/external/callback?code=<long string> request seems to be failing every time. Nothing in the logs to troubleshoot so I'm not sure what to try next! Thanks in advance for any help.