External URL works from browser bur not from iOS app

I have configured an external url with a reverse proxy (netscaler) wich also is doing SSL Offload Internal url is http. External url is https.

Browser works witn internal url and external url
iOS app works only with internal url but not with external url.

Any ideas why?

Post what you’re using in both places

Internal:
http://IP:8123

External:
https://hass.domain.com:8443
this works for internal also when Im on Wifi.

Does the app maybe not work with a custom port other than 443?