invalid_grant - oauth#token API v2

[vaibhavdeepP]

Using ProductHunt API for authenticating user.

Step 1:
Followed this https://api.producthunt.com/v2/docs/oauth_user_authentication/oauth_authorize_ask_for_access_grant_code_on_behalf_of_the_user and received access_grant as code in the callback URl.

Step 2:
Following this https://api.producthunt.com/v2/docs/oauth_user_authentication/oauth_token_use_the_access_grant_code_you_received_through_the_redirect_to_request_an_access_token

with the payload as

{
    "client_id": "CLIENT_ID",
    "client_secret": "CLIENT_SECRET",
    "redirect_uri": "REDIRECT_URI,
    "code": "jEIysGnrMNFJoNZuCYGFm3luVpAz_5q7x_MAYdcDzz8",
    "grant_type": "authorization_code"
}

This POST request throws this error -

{
    "error": "invalid_grant",
    "error_description": "The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client."
}

I've checked the code and REDIRECT_URI matches exactly with the one specified in the API Dashboard.

Why am I still getting this error?