OAuth2 access token request invalid - grant_type expecting \"authorization_code"\

Thank you Greg!

I am trying to list the files (/get_metadata) in my app folder but for some reason I can't set up the correct path. Take a look at this message:

{"error_summary": "path/not_found/", "error": {".tag": "path", "path": {".tag": "not_found"}}}

The app folder was automatically created by Dropbox, and after that I created a txt file named text.txt inside it. As you can see, this is the path:

However, when I send the /get_metadata request via curl I receive the error message that the path dosen't exist.

This is the json file - named getMetadata.json - with the parameters:

{
    "path": "/home/Aplicativos/optisurface",
    "include_media_info": false,
    "include_deleted": false,
    "include_has_explicit_shared_members": false
}

This is the curl request I am using:

<?php 

require_once 'Functions/functions.php';

$token = getToken($_SESSION['uid']);

$data  = file_get_contents('json/getMetadata.json');

	$ch = curl_init();
    
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, "POST");
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Authorization: Bearer ' . $token[0]->itoken, 'Content-Type: application/json'));
    curl_setopt($ch, CURLOPT_URL, "https://api.dropboxapi.com/2/files/get_metadata");
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    
    $response = curl_exec($ch);

    echo '<pre>';
    print_r($response);
    echo '</pre>';

 ?>

Can you help me saying what am I doing wrong?