Hello @anissa,
Thanks for asking. 
Here is the the content of item-skin.class.php file. You can compare this to what you have on your setup. In case if you don’t want to take this route, then you can also try reinstalling the plugin.
<?php
/**
* @package The_Grid
* @author Themeone <themeone.master@gmail.com>
* @copyright 2015 Themeone
*/
// Exit if accessed directly
if (!defined('ABSPATH')) {
exit;
}
class The_Grid_Register_Item_Skin {
private $skins = array();
function __construct() {
$this->skins = apply_filters( 'tg_register_item_skin', $this->skins );
$register = array();
if (is_array($this->skins)) {
foreach($this->skins as $skin => $data) {
$name = (is_array($data) && !empty($data)) ? $skin : $data;
$data = (is_array($data) && !empty($data)) ? $data : '';
$register[$name] = array(
'name' => (isset($data['name']) && !empty($data['name'])) ? $data['name'] : $name,
'filter' => (isset($data['filter']) && !empty($data['filter'])) ? $data['filter'] : 'Standard',
'col' => (isset($data['col']) && !empty($data['col'])) ? $data['col'] : 1,
'row' => (isset($data['row']) && !empty($data['row'])) ? $data['row'] : 1,
);
}
$this->skins = $register;
} else {
$this->skins = array();
}
}
// get skin array
function get_registered_skins() {
return $this->skins;
}
}
add_filter('tg_register_item_skin', function($skins){
$skins = array(
// grid skins
'alofi',
'apia',
'bogota' => array(
'filter' => 'Instagram'
),
'brasilia',
'camberra',
'caracas',
'dacca',
'honiara',
'lisboa',
'lome',
'malabo',
'male',
'maputo' => array(
'filter' => 'Instagram'
),
'oslo',
'podgorica' => array(
'filter' => 'Youtube/Vimeo'
),
'pracia',
'roma',
'sofia',
'suva' => array(
'filter' => 'Woocommerce'
),
// masonry skins
'doha',
'kampala',
'lima',
'lusaka',
'maren',
'panama',
'praia',
'quito',
'riga',
'sanaa' => array(
'filter' => 'Woocommerce'
),
'victoria' => array(
'filter' => 'Youtube/Vimeo'
),
'vaduz' => array(
'filter' => 'Youtube/Vimeo'
),
);
return $skins;
});
class The_Grid_Item_Skin {
private $skins = array();
function __construct() {
$this->skins = apply_filters( 'tg_add_item_skin', $this->skins );
}
// get skin array
function get_skin_names() {
return $this->skins;
}
}
add_filter('tg_add_item_skin', function($skins){
// get upload dir for custom skins
$wp_upload_dir = wp_upload_dir();
$wp_theme_dir = get_stylesheet_directory();
// register all paths where skins can be stored
$paths = array(
// dir path for native skins
TG_PLUGIN_PATH . 'includes/item-skins/grid/',
TG_PLUGIN_PATH . 'includes/item-skins/masonry/',
// dir path for theme skins
$wp_theme_dir . '/the-grid/grid/',
$wp_theme_dir . '/the-grid/masonry/',
);
// get all registered skins
$register_skins_base = new The_Grid_Register_Item_Skin();
$register_skins = $register_skins_base->get_registered_skins();
// get all skin sluf (folder name)
foreach ($paths as $path) {
// get all folders from current path
$folders = (is_dir($path)) ? array_diff(scandir($path), array('.', '..')) : array();
// for each folder register skin
foreach ($folders as $slug) {
// if the skin was registered or custom skin from wp_upload_dir
if (array_key_exists($slug, $register_skins) || strpos($path, $wp_upload_dir['basedir']) !== false) {
// construct php & css files paths
$php = $path.$slug.'/'.$slug.'.php';
$css = $path.$slug.'/'.$slug.'.css';
$skins[$slug] = array(
'type' => basename($path),
'slug' => $slug,
'filter' => (isset($register_skins[$slug]['filter'])) ? $register_skins[$slug]['filter'] : 'Standard',
'name' => (isset($register_skins[$slug]['name'])) ? $register_skins[$slug]['name'] : $slug,
'col' => (isset($register_skins[$slug]['col'])) ? $register_skins[$slug]['col'] : 1,
'row' => (isset($register_skins[$slug]['row'])) ? $register_skins[$slug]['row'] : 1,
'php' => $php,
'css' => $css
);
}
}
}
if (The_Grid_Base::get_purchase_code()) {
// fetch custom skins
$custom_skins = The_Grid_Custom_Table::get_skin_params();
// reassigned custom skin name and params
foreach ($custom_skins as $custom_skin) {
$params = (isset($custom_skin['params'])) ? json_decode($custom_skin['params'], true) : null;
$params['id'] = (isset($custom_skin['id']) && is_array($params)) ? $custom_skin['id'] : null;
if ($params && isset($params['slug'])) {
$skins[$params['slug']] = $params;
}
}
}
return $skins;
});
Thanks.