We have configured the ArcGIS Server and Portal for ArcGIS in a single machine. Where Portal for ArcGIS is configured with Web Adaptor in HTTP 80 port & HTTPS 443 and ArcGIS Server Manager is configured with Web Adaptor in HTTP 81 port & HTTPS 447. Since when we assigned the domain name we made reverse proxy for the Portal for ArcGIS in Port 81. Both Portal for ArcGIS & Server Manager work good. But the REST services we published in Server can't be accessed in the Portal for ArcGIS web map when added via the ArcGIS Server web service.
Throws the following error -
Unable to access the authentication service