adding two screenshots, one of the log , and one of how the widget is rendered, it says something about "invalid css" but i'm not sure it is actual error due to the 302 and 401 and also becuase the widget shows correctly on iframe or in dev-hub (single configuration)
Re: extension in mashup permission/authentication issue
Seems like there is a problem with loading json files. These are widget-specific, there are no json files in extensions (well you could add one yourself, but I don't think it's common). Not sure why you would need them in a mashup though, they are mostly for the property panel. How do you load them? app.getObject() ??
You should probably report this to support and se if they have a solution for you.
Erik Wetterberg https://extendingqlik.upper88.com/