HA redirecting to 404 after auth when adding to Google home

[mossy stirrup]

Hey there!

I'm setting up the Google assistant integration, and after I add my [test] Home Assistant project to Google Home, it sends me to my home assistant instance, I sign in, then it sends me to a 404. It's redirecting me to a url like this:

https://oauth-redirect.googleusercontent.com/a/com.google.android.apps.chromecast.app?redirect_state=<LONG STRING>&state=<LONG-STRING>&service=<MY PROJECT ID>_dev

I was a bit thrown off by the com.google.android.apps.chromecase.app. I verified that my OAuth Client ID is https://oauth-redirect.googleusercontent.com/r/<MY PROJECT ID> and my token URLs are correct because I'm getting directed to my instance to sign in

Any ideas?

[meager venture]

check dns and internal network, reboot

and temp disable ipv6 in HA

[mossy stirrup]

I've verified that I'm connecting to my instance via ipv4. I should note its running with ddns from CloudFlare (with forwarding only), to my nginx instance where the request is forwarded to my server at 192.168.2.10:8123