400 Bad Request response from the token endpoint. This often happens when developers reuse an old or already-used authorization code.
It is likely one of the following issues:
Authorization Code can only be used once
Each authorization code is single-use only. If the first request to exchange the code for an access token fails (even due to an invalid parameter or network issue), the code becomes invalid and cannot be reused.
application/x-www-form-urlencoded).