Troubleshoot Directus by adding this as a custom extension. See if you've missed any of the requirements.

troubleshoot.php

<?php

use Directus\Application\Http\Request;
use Directus\Application\Http\Response;

return [
    '' => [
        'method' => 'GET',
        'handler' => function (Request $request, Response $response) {
            // Simple GET endpoint example
            return $response->withJson([
                'data' => [
                    // Other things to check: mod_rewrite, mysql_version, http_server
                    'php_version' => [
                        'status' => phpversion() >= 7.1 ? true : false,
                        'title' => 'PHP Version',
                        'description' => 'Directus requires PHP 7.1+, though we recommend using the most recent/stable version possible.'
                    ],
                    // Directory Permissions
                    'logs' => [
                        'status' => is_writeable('../logs'),
                        'title' => 'Logs Directory',
                        'description' => 'The logs directory should have write permission'
                    ],
                    'uploads' => [
                        'status' => is_writeable('./uploads'),
                        'title' => 'Uploads Directory',
                        'description' => 'The logs directory (/public/uploads) should have write permission:  (or your configured upload directory)'
                    ],
                    // Extensions
                    'pdo' => [
                        'status' => extension_loaded ('pdo'),
                        'name' => 'pdo + mysql',
                        'description' => 'PHP Data Objects (PDO) enables safer parameterized queries'
                    ],
                    'curl' => [
                        'status' => extension_loaded ('curl'),
                        'name' => 'cURL',
                        'description' => 'cURL fetches metadata (eg: title and thumbnail) from embed services like YouTube and Vimeo'
                    ],
                    'gd' => [
                        'status' => extension_loaded ('gd'),
                        'name' => 'GD Library',
                        'description' => 'GD allows the Thumbnailer to generate images. To add thumbnail support for SVG, PDF, PSD and TIF/TIFF you must also install the imagick extension.'
                    ],
                    'fileinfo' => [
                        'status' => extension_loaded ('fileinfo'),
                        'name' => 'fileInfo',
                        'description' => 'Fetches metadata (eg: charset and file-type) and IPTC Info (eg: location and keywords) for uploaded images.'
                    ],
                    'mbstring' => [
                        'status' => extension_loaded ('mbstring'),
                        'name' => 'mbstring',
                        'description' => 'The multibyte string functions helps php to work multibyte encoding. These functions are used by Directus to get the correct string\'s length or a correct comparison with another string.'
                    ],
                    'xml' => [
                        'status' => extension_loaded ('xml'),
                        'name' => 'xml',
                        'description' => 'Used by PHPUnit (Only required if you are installing PHPUnit)'
                    ],
                ]
            ]);
        }
    ],
];