External library installed but failed to load

Hi,

I'm trying to load the TinyButStrong library into my custom module, but it won't get loaded.
The hook libraries_load returns an array but the key 'loaded' is set to 0.
When I execute the hook_libraries_detect everything looks fine and the key 'installed' is set to TRUE.

The original TinyButStrong library is placed in sites/all/libraries into the folder 'tbs_us'.

function stapp_documents_libraries_info() {

  // A very simple library. No changing APIs (hence, no versions), no variants.
  // Expected to be extracted into 'sites/all/libraries/simple'.
  $libraries['tbs_us'] = array(
    'name' => 'TinyButStrong',
    'vendor url' => 'http://example.com/simple',
    'download url' => 'http://example.com/simple',
    'version callback' => 'stapp_documents_version_callback',
    'files' => array(
      'php' => array('tbs_us.php'), //this can be a path to the file location like array('lib/simple.js')
    ),
  );

  return $libraries;
}

function stapp_documents_version_callback() {
  //use some fancy magic to get the version number... or don't
  return TRUE;
}

function stapp_documents_documents_page() {
	$name = 'tbs_us';
	
	if (($library = libraries_detect($name)) && !empty($library['installed'])) {
  	dpm('The library is installed. Awesome!');

		// Try to load the library and check if that worked.
		if (($library = libraries_load($name)) && !empty($library['loaded'])) {
		  dpm('The library is loaded. Awesome!');
		}
	}
	else {
	  $error = $library['error'];
	  // This contains a detailed (localized) error message.
	  $error_message = $library['error message'];
	  dpm($error);
	  dpm($error_message);
	}
	

	//require_once(DRUPAL_ROOT . '/sites/all/libraries/tbs_us/tbs_class.php');
	//$tbs = new clsTinyButStrong; dpm($tbs);
  return 'documents';
}

Thanks in advance.

P.S. Regular require_once does work