Regarding Invalid Client on jackhenry DMZ loan Vantage Postman Collection to get access token

I am getting error invalid client as you can see in the attached screenshot, despite after entering the Client_id and Client_secret I should be able to get the access token but getting again and again :-

{

    "error": "invalid client"

}

does anybody have an idea of this error, because without the access token I won't be able to proceed further so if anyone has any idea or has consumed this, suggest me it would be very helpful

For more information I am attaching the Url:-

https://jackhenry.dev/jxchange-rest/providers/loanvantage/api-reference/#/Document/DocumentCreate

Also I am attaching the screenshot of the documentation of LoanVantage DMZ that I have imported in postman as per the guidelines in the documentation.