Android | Companion app "network error"/ unable to log in [February 2024]

Solution found :smile:
My WLAN-router had IPv6 deactivated => set IPv6 on router to “auto-detect”, then disconnected and reconnected WLAN on mobile, and my companion apps works again with WLAN!
(Further infos: In fact, my ISP does not provide IPv6. So I see now that with the setting “auto-detect”, the router uses “6to4 tunnel”, which seems to resolve the problem).
So happy I am back to Companion app. Hope this will resolve the problem for others too.