OTDS REST Push Connector API exception occurring

We created a REST (Generic) syncronization connector by using C# WCF REST service that returns json for the content type. 

When our service handles the request for the POST to the UriTemplate /auth and return a response such as {"token":"valid164943823498"}

we get the following error:

java.lang.RuntimeException: Test Connection failed with: A message body reader for Java class com.opentext.otds.connectors.rest.AuthResponse, and Java type class com.opentext.otds.connectors.rest.AuthResponse, and MIME media type text/html; charset=utf-8 was not found.

Below is the Raw response from the auth method

HTTP/1.1 200 OK

Cache-Control: private

Content-Type: application/json; charset=utf-8

Server: Microsoft-IIS/10.0

X-AspNet-Version: 4.0.30319

X-Powered-By: ASP.NET

Date: Wed, 18 Nov 2020 20:28:05 GMT

Content-Length: 29

{"token":"valid164943823498"}

How do we get passed the RuntimeException that OTDS is throwing?