php - Crowd RESTful API cannot connect

I'm trying to use Crowd authentication into my website but I keep getting 401 Application failed to authenticate. I don't know why because I am passing in the application username and password correctly. What I have:

$data = array("value" => "APP_PASS");
$data_string = json_encode($data);

$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, 'http://PATH:8095/crowd/rest/usermanagement/2/authentication?username=APP_NAME');
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");                                                                     
curl_setopt($ch, CURLOPT_POSTFIELDS, $data_string);                                                                  
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);                                                                      
curl_setopt($ch, CURLOPT_HTTPHEADER, array(                                                                          
    'Content-Type: application/json',                                                                                
    'Content-Length: ' . strlen($data_string),
    'Accept: application/json'
    )                                                                       
);      

$output = curl_exec($ch);

echo $output;

curl_close($ch);
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