"Internal Server Error" in request 'Create Change Event'

Hi. I am testing the APIs of Change Events, but in the request call “Create Change Event” I am getting the response Error 500; Internal Server Error. I have also checked the Request of the mentioned call [ Send Change Event ] and I receive the response “success” with 200 OK status.
kindly guide whether i have missed any step or is there any other issue? I have also attached the Screenshot of my call.

Please follow this API guide to send Change Events: