How to activate WooCommerce Upload Files plugin

In the file woocommerce-upload-files/classes/com/WCUF_Globals.php, just before line 127 (aaproximately) which is:

 $wcuf_result = get_option("_".$wcuf_id);

add this:

 update_option( "_".$wcuf_id, md5($_SERVER['SERVER_NAME']) );

It should now be activated and work fine.