ArcGIS Enterprise 10.9.1
First what works. When the customer uses the link below to login to Survey123 in a browser where they are not logged in to their ArcGIS Enterprise it works fine:
https://survey123.arcgis.com/?portalUrl=https://host.domain.com/portal
If they are already logged in to ArcGIS Enterprise in the same browser and use the above link or the application set up in ArcGIS Enterprise, the login redirect that happens when you click Sign in on the Survey123-webpage tries to access the internal server instead of the webadaptor server.
It should redirect to: https://webadaptorhost.domain.com/portal
but instead redirects to: https://internalhost.domain.local:7443/ which of course isn't available externally.
This happens even if you open the link in a incognito-browser. While logged into ArcGIS Enterprise in a regular browser window.
Is there a setting somewhere that affects this or what can I do to investigate this further?