swagger-ui returns 500 after deployment

thank you @VisualBean.

As it was not so obvious for me .... how to... a simple image.

In Project > Your Project properties > Build Tab

Swashbuckle is hiding the real error message due to your customErrors setting in web.config. If you set customErrors to off you should get a better error message.

<system.web>
    <customErrors mode="Off"/>
</system.web>

When debugging I was using the debug config (Which I had generated XmlComments for: Properties -> build tab -> Output -> XML Documentation File)

I had not done this for my release configuration (duh...) - now everything works