Invalid user error

yes @Aravind it is the same sprout account but few days back even it sprout account the reply was working fine, suddenly it stops working

Araving S,

yes i am replying with the same user who created the ticket with the same API but still i am getting this error. as mentioned in the above the user "Sora" created a ticket and with the same user (Sora) is replying back to the agent.

$reply_data = json_encode(array(
"body" => "Thanks Admin, i am waiting for your good response ...",
"user_id" => 42002034395,
));

$url = "https://$yourdomain.freshdesk.com/api/v2/tickets/12/reply";;

$ch = curl_init($url);

$header[] = "Content-type: multipart/form-data";
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_USERPWD, "$api_key:$password");
curl_setopt($ch, CURLOPT_POSTFIELDS, $reply_data);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$server_output = curl_exec($ch);

$info = curl_getinfo($ch);

$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$headers = substr($server_output, 0, $header_size);
$response = $server_output;

if($info['http_code'] == 201) {
echo "Reply has been posted, the response is given below."."<br>";
echo '<pre>', print_r(json_decode($response));
} else {
if($info['http_code'] == 404) {
echo "Error, Please check the end point \n";
} else {
echo'<pre>';print_r($response);
}
}

curl_close($ch);

 here is the code, please guide me if there is any code error

But it was working fine few days back with the same code even though the account was sprout,i am confused because it stop working suddenly. the API key you are talking about is the same we get in the profile settings of the domain . right?

let me add one more thing if it helps you out to understand my issue, right now i am not having any other Agent just the admin, And the admin is the one who is facilitating the tickets on my trail account