I’m new here and new to Home Assistant since a few weeks. I got everything running smoothly but there is this one thing that bugs me and I cannot find a solution searching the community and the web.
HA is running behind a Fritz!Box 6590 Cable which is up to date and not limited by my ISP. I also have a Fritz!Powerline 1260E running and Home Assistant on a Raspberry PI is connected to it by LAN.
I’ve set up DuckDNS with Letsencrypt from Supervisor as described, it is running without any issues while accessing HA within the local WiFi from my computer, but it has some issues from my mobile phone. It won’t connect to it showing some connection errors until I go up to my computer, access HA by Browser and … Voila! In the very same moment, the HA Companion App is able to connect, too. So… What??? I will work for while and loose the ability to connect then until I reconnect to HA in my Computers Browser (or disable WiFi to get connection from “outside”).
This can be reproduced that on 2 different mobiles (both running on Android, a Samsung Galaxy S10 and Google Pixel 2).
I checked the documentation on Companion App Networking and Hairpin NAT. I applied a DNS Rebind Protection exception for the complete domain name (xyz.duckdns.org) and then I restarted everything (just to make sure, …).
Port sharing is activated for 18123 forwarding to internal HA Port 8123 of the LAN IP address of the raspberry. WiFi is also enabled there but more or less to have another option to access it, just in case…
Does anyone have an idea, how to solve that?
Here some information about the configuration:
lets_encrypt: accept_terms: true certfile: fullchain.pem keyfile: privkey.pem token: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx domains: - xyz.duckdns.org aliases:  seconds: 300
http settings in configuration.yaml
http: ssl_certificate: /ssl/fullchain.pem ssl_key: /ssl/privkey.pem ip_ban_enabled: true login_attempts_threshold: 4
I can provide more information, if helpful.
Thanks in advance and best regards