I get code and access token but i cannot call API function

My url being generated https://api.stackexchange.com/2.2/me?site=stackoverflow&access_token=lcynp67rMHfm%28DRLjv7CVQ%29%29&key=6521

 {
  "error_id": 400,
  "error_message": "`key` doesn't match a known application",
  "error_name": "bad_parameter"
}

Client Id

6521 This Id identifies your application to the Stack Exchange API. Your application client id is not secret, and may be safely embeded in distributed binaries.

Pass this as client_id in our OAuth 2.0 flow.

Socialite Provider Link http://socialiteproviders.github.io/providers/stackexchange/

Thanks in advance