Android Companion App stopped connecting via reverse proxy

Hi,

for some months, I had a perfectly working setup:

HA internally on http://192.168.xx.xx:8123
deSec dynamic domain name for HA ponting to the ip of may firewall (OPNsense)

On the OPNsense, there is a HAproxy running, listening on port 8443, which does the SSL offloading and then calling the internal URL, so the external URL is
https://homeassistant.my.own.doman:8443

Worked for months.

Since a few days, it stopped working with the HA Android Companion App.

Internal connections are totally fine, both browser and companion app

External connections to homeassistant.my.own.doman:8443 wok perfectly fine with Chrome browser on Android (severl different phones with different Android versions)

however: they do NOT work any more with the companion app - on the same phones where the same URL called with the Chrome browser works totally fine at the same time.

(no update on OPNsense in the meantime, no config changes on the HA proxy setup)

the companion logs only states:
using external URL
WebSocket: could not authenticate

well, yes, I knew that already.

But I can authenticate using Chrome and the exact same URL on the same device …

happens on 4 different Android devices …

Any ideas?

Settings > companion app > logs

Look at the failure for tips on how to resolve.