Trying to publish to my wall, getting "Insufficient permission" error - facebook-graph-api

Question

I am using the following code post to my timeline. I am getting an error which is shown at the end of this post. Any ideas?
<?php
......
$request = 'https://graph.facebook.com/oauth/access_token';
$grant_type = 'client_credentials';
$client_id = '1504901xxxxxxxx'; //FaceBook Developer App_id LIVE
$client_secret = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'; //Facebook Developer Api_secret LIVE
$postargs = 'grant_type=' . urlencode($grant_type) . '&client_id=' . $client_id . '&client_secret=' . $client_secret;
curl_setopt($session, CURLOPT_POST, true);
curl_setopt($session, CURLOPT_POSTFIELDS, $postargs);
curl_setopt($session, CURLOPT_HEADER, false);
curl_setopt($session, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($session);
preg_match('/access_token=(.*)/', $response, $match);
curl_close($session);
$access_token = trim($match[1]);
$Application = 'WTSO';
$User = '1504901xxxxxxxx'; /*this is the user id*/
$target_id = '1647886xxxxxxxx';
$api_url = 'https://api.facebook.com/method/stream.publish?';
$server_loc = 'https://wtso.com';
$logo = new stdClass();
$attachment = new stdClass();
$logo->type = 'image';
$logo->src = 'http://admin.wtso.com' . '/images/' . (($new_products['image_name']) ? $new_products['image_name'] : 'xx1235.jpg');
$logo->href = $facebook_bitly;
$attachment->name = ' '; //'WTSO Product Notification';
$attachment->caption = (!empty($new_products['products_short_description'])) ? substr(strip_tags($new_products['products_short_description']), 0, 900) : $facebookText;
$attachment->description = ' ';
$attachment->href = $facebook_bitly;
$attachment->media = array($logo);
$message = (!empty($facebookText)) ? strip_tags($facebookText) : $new_products['products_name'];
$postargs2 = 'message=' . urlencode($message) . '&attachment=' . urlencode(json_encode($attachment)) . '&target_id=' . urlencode($target_id) . '&access_token=' . urlencode($access_token) . '&method=stream.publish';
$request2 = $api_url . $postargs2;
//Initiating a 2nd Curl instance
$session2 = curl_init($request2);
curl_setopt($session2, CURLOPT_HEADER, false);
curl_setopt($session2, CURLOPT_RETURNTRANSFER, true);
$response2 = curl_exec($session2);
curl_close($session2);
?>
I am getting this error from Facebook in $response2
<error_code>200</error_code>
<error_msg>Insufficient permission to post to target on behalf of the viewer</error_msg>