Vanilla config - problems getting IOS app to work - IP6 issue?

I’ve been using HA for a long time (and was a very active contributer a while back).

My HA has been super stable running on a Mac Mini - but increasing I think my config is old and getting likely to be unsupported - so I wanted to move to something more modern and vanilla.

So far so good - a Pi3 B running standard build HassOS - all as described on the “Getting Started” page. Everything working with the integrations etc. I will take care over moving my automations etc as I’ll try and use the new config gui.

However I’m having problems getting the IOS app to work. I actually still have both HA servers running - and I can authenticate to the MAcOS one no problem - having if I try to authenticate to the HassOS one I get the dreaded “invalid client id or redirect url”

The logs say:-

2020-05-18 17:22:06 ERROR (MainThread) [homeassistant.components.auth.indieauth] Timeout while looking up redirect_uri
2020-05-18 17:22:06 WARNING (MainThread) [homeassistant.components.http.ban] Login attempt or request with invalid authentication from

Looking at the support forums it would seem this could be IP6 related - although I stress this is the current standard build. How would I go at resolving this?

So my ifconfig doesn’t have anything IPv6 running - so don’t think it’s IPv6 related.

Advice very welcome!

In case anyone else come across this

ha dns options --servers dns:// --servers dns://

Fixes it.

Not sure what the DNS issue was.