No OWIN authentication manager is associated with the request.

Hi guys,

I want to add an Web API end point to my episerver project. I have set up the URL end point by following these simple steps.

https://world.episerver.com/blogs/rejaie-johnson/dates/2017/5/episerver-cms--web-api/

However when I try and access my end point URL I get the following error:
No OWIN authentication manager is associated with the request.

I have tried 

adding this line to my WebConfig

<add key="owin:AutomaticAppStartup" value="true"/>

But I get the same error.

The API will return a PDF file based on some paramerters and is public facing so needs no Authentication as such.

Any ideas? -