Getting 404 error while getting access token from API

Hi,

We are getting 404 error while consuming API fro getting access token. We are following as per given in below link. Even passing correct client_id, client_secret, code, grant_type, request_uri it is still throwing error. Can anyone guide us on this.

https://helpx.adobe.com/sign/kb/how-to-create-access-token-using-postman-adobe-sign.html

Thanks in advance

Husain