Try to enable from the web.config file under <system.webserver></system.webserver> like so:
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="*" />
<add name="Access-Control-Allow-Credentials" value="true"/>
<add name="Access-Control-Allow-Headers" value="Content-Type" />
<add name="Access-Control-Allow-Methods" value="GET, POST, PUT, OPTIONS" />
</customHeaders>
</httpProtocol>
To handle the preflight request error add the line below in the <handlers></handlers> tags:
<add name="OPTIONSVerbHandler" path="*" verb="OPTIONS" modules="ProtocolSupportModule" requireAccess="None" responseBufferLimit="4194304" />
Then in the Global.asax file, add the following method:
protected void Application_BeginRequest(object sender, EventArgs e)
{
if (HttpContext.Current.Request.HttpMethod == "OPTIONS")
{
HttpContext.Current.Response.Flush();
}
}