@Tushar take a look through this post:
Follow through and use the example BPMN file. There are also some updates further down in the thread so make those changes to the BPMN file. Replace the sample URL in the BPMN file with your URL. If it does not work then you have a issue with your URL. The example in the post works and has worked for multiple people with similar issues as you described.
Likely you have a config issue in your BPMN.