I've recently installed Portal onto a new server that is federated with a separate GIS Server. The server environment is a "default deny" type of environment which I will come back to in a moment after describing the issue.
If one tries to create a new app using Web App Builder (From the Portal page under My Content), as soon as one fills the title tags and summary and clicks submit, it first shows the loading screen for the Web App Builder for a very brief period and then redirects to sign the user out automatically instead.
If I have Developer Tools logging this while running, firstly I see the following warning in Chrome before even starting up web app builder (using Chrome) when I log in and go to My Content:
Refused to execute script from 'https://[website URL]/portal/sharing/proxy?https://[GIS Server Machine Name]:6443/arcgis/admin/data/findItems?managed=true&f=json&token=[Token]&callback=dojo.io.script.jsonp_dojoIoScript1._jsonpCallback' because its MIME type ('text/plain') is not executable, and strict MIME type checking is enabled.
When I click through to create a new Web App, I get this similar warning in the console:
Refused to execute script from 'https://[Website_URL]/portal/sharing/rest/portals/self?f=json&token=[Token]&callback=dojo_request_script_callbacks.dojo_request_script0' because its MIME type ('text/plain') is not executable, and strict MIME type checking is enabled.
Anyone run into this issue themselves and have hints on how to proceed?
My thought is that it may be related to pulling/running external scripts... The ArcGIS Server machine is limited from the internet with only whitelisted ports, for instance. Aside from that, I did notice that Web App Builder uses self-signed certificates, which may be an issue as well? Before speculating I wanted to see if anyone else has input.
I did find a similar question here: ArcGIS Web Application Template / Portal Issue