I've been trying to generate my access token in the Acumatcia platform using the Authorization code flow but i am unable to generate it as it is raising me an error invalid client i have also tried the Resource owner password flow but still it is giving me the same error invalid client. I have generated the access code but when i am using that access code in authorization flow it is giving me an error .
I have followed all the steps as told in their Acumatica Integration guide and made an client application in the acumatica , generated the client id and client secret.

Here i am using the post request to send in the request and is using the redirect uri of the postman only.
By using the GET method i have generated the Authorization Code and was successful in it.

Can anyone help me to resolve the issue of invalid client ?