If you're hosting your API on a different domain to your app, such as api.domain.com, you may be hitting into some cross-origin request roadblocks. In IIS, this is pretty easy to fix -- or well -- disable.
In your WebAPI project's web.config, put in the following:
<httpProtocol> <customHeaders> <add name="Access-Control-Allow-Origin" value="*" /> <add name="Access-Control-Allow-Headers" value="Origin, X-Requested-With, Content-Type, Accept" /> </customHeaders> </httpProtocol>
This will enable cross-origin resource sharing (CORS) and allow you to get back to work.