LWA : Not able to exchange Authorization Code for AccessToken : invalid_grant

Question

I am trying to implement LWA in an Alexa Skill (Accept Grant so to send events to the Alexa). I have already done this successfully in the past in a published skill, so I just made a new security profile on LWA console, copied the client_id and client_secret and formed the request as :

const data = {
  "grant_type": grant_type,
  "client_id": client_id,
  "client_secret": client_secret,
  "code": code,
};

let authResponse = await axios.post(url, data,
  {headers: {'content-type': 'application/x-www-form-urlencoded'}}
);

I am getting the following error message : 400 Bad Request :

{
    "error_description": "The request has an invalid grant parameter : code",
    "error": "invalid_grant"
}

The client_id and client_secret I have added from the LWA Developer Console security settings for my domain. I can't understand why am I facing this error. 'Code' i have got from the AcceptGrant directive and grant_type is 'authorization_code'. Can anyone help me with this?

Also : In my published skill, where this works flawlessly, the client_id and client_secret mentioned in the Lambda function are different from the values mentioned in the LWA security settings for that domain, I am not sure why is this so, because I remember using the values from the LWA security settings, do these values change over time?

Answer 1

Amazon's docs gives essentially 2 reasons for the error code "invalid grant".

invalid_grant   The authorization code is invalid, expired, revoked, or was issued to a different client_id.

Either the authorization code is no good or the client ID sent with the authorization request is different than here in the token request.

https://developer.amazon.com/docs/login-with-amazon/authorization-code-grant.html#access-token-errors