While generating the JWT token, Please include the unique partner Id in new partner registration process in the request body of the token request.

Example:

{
"claims" : 
    { 
      "subject" : "{partner-id}"
    }
}

Making the API call, we need to pass the unique partner Id used for generating the token as Request Header "claims" of the API.

Example:

claims = {"claims" : {"subject" : "{partner-id}"}}
Where I can find Partner ID?

Partner ID is available on the top of My Apps and App Details page.