Error when extern but Browser works (extern_auth=1)

Hey there,
I have a weird problem and couldn’t find any documentation, forum posts, … to that.
This week I finished to configure external access. I shortly explane my environment but I do not think that there is the problem.
My ISP connected us to a CGN so I do not have a public IPv4 address. I have to use IPv6 to get access to my ha vm. For IPv4 devices I use a vServer with public IPv4-address running 6tunnel. That converts all IPv4 traffic to IPv6. Also DNS is configured to work proberly. Now I can access my HomeAssistant from everywhere through a browser by just typing like ha.example.com:8123 (but with my domain). Does work from phone (using Chrome) and from PC (using Chrome, Firefox, Edge, …).
In the android app I configured the local IP-address once. Now I wanted to change the address to my public DNS so I can also use it when not at home. Furthermore I added SSID of my home wifi network and entered the local IP of HA in the internal-textfield below.
When connecting via wifi it works. when connecting via mobile network it says that it wasn’t able to get connection. I try to translate my error message as good as possible:

Website not available
Website https://ha.example.com:8123/?external_auth=1 couldn't load.
net::ERR_NAME_NOT_RESOLVED

Name not resolved sounds like issue in DNS but as I said I can open HA in browser even via mobile phone network.

I would be very grateful if someone has an idea, a solution suggestion or approaches.

Thanks
soberz

Is the cert valid?

Yes, it is. Also as I said I can connect to HA via Browsers. I don’t see any kind problem with that. But thanks for your answer

well if you replied back saying you had to accept the SSL prompt in a browser then I would say that would not work but since the SSL cert is valid you shouldn’t be facing that prompt.

Try the tips here: https://companion.home-assistant.io/docs/troubleshooting/networking

Okay I’ve read this tips website. In my opinion there is nothing I can improve. As mentioned I already solved the problem of beeing in a CGN with own solutions (vServer that takes IPv4 traffic and sends it over IPv6 even carrying the http header in my network) and have DNS assigned (A record pointing to vServer, AAAA record pointing to my network). I forgot to mention that my Firewall does the encrypting for homeassistant. But I don’t think it makes a difference in that point. If logging in from browsers didn’t work neither, I’d say the problem is in the firewall. But I can connect from browsers from anywhere.

I have the same problem as soberz, I connect well from internet browsers, but not possible through the Companion application.
I use “cloudflare” to allow connect from internet: addon-cloudflared/DOCS.md at 71ca76cbbbd8219100748386fb53a87a2a1863ce · brenner-tobias/addon-cloudflared · GitHub

Any solution here? I am having same issue…

having the same issues here. its intermittent, but seems to be happening more.

getting the following :
websocket failed
uncaught (promise)
GET Net:: ERR_FAILED
POST net:: ERR_NAME_NOT_RESOLVED

suggests a local DNS error

problematic as I’m running ad guard home on the machine I can’t reach…

does a browser work?

local IP access works, outside access doesn’t. I will have to check next time if I can access through cellular to eliminate the local dns issue. Thanks for the insight.