HTTP Client destination with Salesforce not working

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While connect Salesforce with HTTP Client to write the data as JSON object, I am getting the below OAuth2 exception. But the credentials and the Client id and Security id are correct and verified on the Salesforce side with POSTMAN application, we are getting the response using the same details.

HTTP_21 - OAuth2 authentication failed. Please make sure the credentials are valid

Can anyone help on this issue at the earliest?

Thanks, Johnson.