Why $wpdb->insert and $wpdb->update not working server but it is working in localhost?

I am working in a wordpress site, I started to work in local enviroment using xampp server.

I used wpdb to do operations with the database like this:

global $  wpdb;     $  name = $  wpdb->get_results("SELECT meta_value FROM wp_usermeta WHERE meta_key = 'first_name' AND user_id = ".$  user." ");      $  wpdb->update(      'wp_usermeta',      array(          'meta_value' => $  v1      ),      array( 'user_id' => $  user, 'meta_key' => 'first_name'  ),      array(          '%s'     ),      array( '%d', '%s')    ); 

In local enviroments works perfectly but when I migrated the project to an amazon instance, Ubuntu server using nginx and all the operations using $ wpdb are not working.

I cant update, I cant insert.

I dont know why.

Any clue?