sharepoint online – AADSTS7000215: Invalid client secret is provided

We are integrating with client’s SharePoint using SharePoint REST API. For this, the client has registered an add-in at their side using the appregnew.aspx and provided permissions to the Add in using appinv.aspx.

Now when I am trying to get the bearer token for using the tenant id and giving all other parameters in request body, I am getting the following error:

 "error": "invalid_client",
 "error_description": "AADSTS7000215: Invalid client secret is provided.rnTrace ID: 993e6c16 
  -68f3-4105-baf5-b08368de0700rnCorrelation ID: 59a5e402-1583-422b-8b62- 
    03b620eb72c1rnTimestamp: 2020-06-04 06:34:01Z"

The error message says the client secret is invalid but it is the same client secret that we got from the appregnew.aspx. Can someone help me with this error?

I am using postman to hit the URL and using the application/x-www-form-urlencoded for request body.

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