WP_REMOTE_POST Requests are being blocked by API provider [closed]

If the API is expecting a JSON object you should change your args to:

$args = array (
    'sslverify' => false,
    'data_format' => 'body',
    'headers' => [
        'Authorization: Bearer {API_KEY}',
        'Content-Type: application/json'
    ],
    'body' => json_encode([
        'region' => 'USA',
        'plan' => 1,
        'label' => 'API Test',
        'app_id' => 2
    ]),
);

• Encode your data into a JSON string
• add data_format=body