Webmethod authentication in ASP.NET Identity

[aspliid]

I am the process of implementing ASP.NET Identity in a Telerik ASP.NET Ajax 2016.1.225 webapplication, due to the client's request for a more modern login (two-factor i.e.)

A few of the comboboxes are using EnableLoadOnDemand, set up with: <WebServiceSettings Method="GetCompanyNames" Path="booker_bestil_service2.aspx" />  

Codebehind signature is:

    [WebMethod(EnableSession = true)]
    public static RadComboBoxData GetCompanyNames(RadComboBoxContext context)

 

After disabling the old formsauthentication, and moving to ASP.NET Identity, this doesn't work. It gives a "Authentication failed", due to the 401 redirect to the login page. Attached is a snip from Fiddler.

How can I setup EnableLoadOnDemand with ASP.NET Identity?

Thanks :-)