Consumer Key is Missing - Sending Grades from External LTI system

My Moodle was migrated to another server in my data center and now mod/lti/service.php is returning:

Exception - Consumer key is missing.

Lines 42 through 54 in the code:

foreach (lti\OAuthUtil::get_headers() as $name => $value) {
    if ($name === 'Authorization') {
        // TODO: Switch to core oauthlib once implemented - MDL-30149.
        $oauthparams = lti\OAuthUtil::split_header($value);

        $consumerkey = $oauthparams['oauth_consumer_key'];
        break;
    }
}

if (empty($consumerkey)) {
    throw new Exception('Consumer key is missing.');
}

This is where the exception is being caught but why and what can I do to diagnose why Moodle is choking here?