Start Workflow from WebService control

Trying to automatically start a workflow using webservice.

below is how my webservice url looks like, connection is successful.

x

below is how my response mapping looks like

sample values for ItemURL and Subscription ID

itemurl : <site url>/Lists/<list name>/<itemid>_.000   (item on which workflow should start)

Subscription id: "{fb5182d8-9bf1-4ed6-8e96-0ff8441a77a6}"   (workflow that needs to be started by webservice)

error message :

ResponseCode: 500 (Internal Server Error) SPRequestGuid:b050549f-e18a-d072-42c1-b61000f216bc request-id:b050549f-e18a-d072-42c1-b61000f216bc X-FRAME-OPTIONS:SAMEORIGIN SPRequestDuration:9 SPIisLatency:0 Persistent-Auth:true MicrosoftSharePointTeamServices:15.0.0.5189 X-Content-Type-Options:nosniff X-MS-InvokeApp:1; RequireReadOnly Content-Length:537 Cache-Control:private Content-Type:text/xml; charset=utf-8 Date:Wed, 20 May 2020 16:15:21 GMT Server:Microsoft-IIS/8.5 X-AspNet-Version:4.0.30319 X-Powered-By:ASP.NET &lt;?xml version="1.0" encoding="utf-16"?&gt; &lt;soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"&gt; &lt;soap:Body&gt; &lt;soap:Fault&gt; &lt;faultcode&gt;soap:Server&lt;/faultcode&gt; &lt;faultstring&gt;Exception of type 'Microsoft.SharePoint.SoapServer.SoapServerException' was thrown.&lt;/faultstring&gt; &lt;detail&gt; &lt;errorstring xmlns="http://schemas.microsoft.com/sharepoint/soap/"&gt;Root element is missing.&lt;/errorstring&gt; &lt;/detail&gt; &lt;/soap:Fault&gt; &lt;/soap:Body&gt; &lt;/soap:Envelope&gt;

Not sure what is missing. I am able to validate and publish the workflow successfully.