PHP Clip Generation/OAUTH Missing

API
2

The access token and client ID need to be specified as a header

Not a query string parameter

An example:

curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Client-ID: ' . CLIENT_ID,
    'Authorization: Bearer ' . $keys->access_token
));

you shouldn’t do BOTH like you have

Additionally, the error suggests you generated the wrong type of token

You need a response_type: code with the required scope attached

but made a response_type: client_credentials