Fiddler not capturing requests from C# application

I was trying to run Fiddler (v4.6.0.2, built August 17, 2015) to capture outgoing requests from a C# WebAPI application (.NET 4.5.2) to Amazon web services.

I have set the proxy configuration in web.config (the application is running under my domain user account) as per the Amazon documentation as well as the Telerik documentation:

<aws region="us-west-2" profileName="xxxxxxxxxxxxxx">
  <proxy host="127.0.0.1" port="8888"/>
</aws>

<system.net>
  <defaultProxy enabled="true">
    <proxy usesystemdefault="False" bypassonlocal="False" proxyaddress="http://127.0.0.1:8888" />
  </defaultProxy>
</system.net>

When Fiddler runs, it dutifully captures all traffic coming from my browser. I know that my application is routing its web requests properly because if I turn Fiddler off, I get exceptions due to being unable to connect to the proxy. However, the problem is none of the application's requests to Amazon are showing up in Fiddler. I turned off all filters in Fiddler to make sure I hadn't accidentally hidden those requests.

I also tried it in a Windows console application and I had the same behavior. Am I missing any other settings? Thanks.