Where to define external URL - HA on Android

Hi there,

I have setup HA as well as external link to it and working fine.
Though in the HA app on Android was setup using my wifi network, I can therefore access HA on my mobile when I am on wifi, but not when I am on the “internet” (understand 4G / 5G …)

there is says the external URL is empty, but I can not enter it as it is grey.

On a computer in the settings it tells the external access is de-activated …

Again, I have open the redurected the ports on my router and if I try my :8123 on a browser it perfectly works … but not on the Androig app

Can so please advise ?
Many thanks !!