I am having issues importing a custom widget into Portal in ArcGIS Enterprise 10.6.1 and I am not sure if I am doing something wrong, or if it is just a limitation of Esri.
When I add the custom widget URL in Portal, after entering the Manifest URL, I receive the following error message: "Unable to load https://<gis.domain.com>/portal/sharing/proxy?https://<apps.domain.com/manifest.json status: 400."
There are two different servers. One that hosts all components ArcGIS Enterprise, and the other which hosts the custom widgets. Both are publicly accessible and the widget URL is fine as I can access it normally through a web browser with no errors. But that URL does not work when I try to import it through Portal.
If I use the machine name URL for the custom widget, Portal is able to import the widget fine. But if I use the publicly accessible URL, it does not work and I receive the error message above.
Any ideas on what could be causing this error message?