I have installed and licensed these on a single EC2 instance in the order given:
- Arcgis server
- Arcgis Datastore
- Validate it with the server
- Arcgis portal
Upon installation of the ArcGIS web adaptor, I created one for the server. Upon configuration, I clicked on the first option for the server. Upon clicking next I get the error:

Not Found
HTTP Error 404. The requested resource is not found.