Youtube Data API v3 Failed to start the resumable upload - php

Question

As of this morning I'm getting this error when trying to upload a Video with the service account and key, this worked at around 6pm yesterday.
I've tried it with both the resumable option set to true and false but to no avail.
This is my code
$client = new Google_Client();
$client->setClientId($OAUTH2_CLIENT_ID);
$key = file_get_contents($KEY_FILE);
$client->setAssertionCredentials(new Google_AssertionCredentials(
$SERVICE_ACCOUNT_NAME,
array('https://www.googleapis.com/auth/youtube'),
$key)
);
$client->setClientSecret($OAUTH2_CLIENT_SECRET);
$redirect = filter_var('http://' . $_SERVER['HTTP_HOST'] . $_SERVER['PHP_SELF'],
FILTER_SANITIZE_URL);
//$client->setRedirectUri($redirect);
$htmlBody = '';
// YouTube object used to make all API requests.
$youtube = new Google_YoutubeService($client);
I get back a valid bearer signature from here but when I initiate the upload I get the following error when setting the non resumable flag to false:
$media = new Google_MediaFileUpload('video/mp4', null, true, $chunkSizeBytes);
"error": {
"errors": [
{
"domain": "youtube.header",
"reason": "youtubeSignupRequired",
"message": "Unauthorized",
"locationType": "header",
"location": "Authorization"
}
],
"code": 401,
"message": "Unauthorized"
}

Answer 1

I hadn't set my access token which referenced the credentials. Make sure you set your access tokens!