I am getting OAuth token when I call this Google Cloud function (using node.js) but it seems that I am not getting the correct OAuth token for messaging.

const MESSAGING_SCOPE = 'https://www.googleapis.com/auth/firebase.messaging';
const SCOPES = [MESSAGING_SCOPE];

function getOAuthAccessToken() {
    return new Promise(function (resolve, reject) {
        let jwtClient = new google.auth.JWT(
            keyData.client_email,
            null,
            keyData.private_key,
            SCOPES,
            null
        );
        jwtClient.authorize(function (err, tokens) {
            if (err) {
                reject(err);
                return;
            }
            resolve(tokens.access_token);
        });
    });
}

//error payload:
- Pretty-JSON-String: {
  "error" : {
    "code" : 400,
    "message" : "The registration token is not a valid FCM registration token",
    "status" : "INVALID_ARGUMENT",
    "details" : [
      {
        "@type" : "type.googleapis.com/google.firebase.fcm.v1.FcmError",
        "errorCode" : "INVALID_ARGUMENT"
      }
    ]
  }
}

Note: I can get it (OAuth access token) in Google playgrounds and it works, but that token is just temp token.

Any input, solution how to get it.