Fix error with product custom fields plugin

The plugin works fine, but the when I add a "long text field", it doesnt detect what I write on it and dont allow me to continue with the purchase.
The plugin is
Advanced Product Fields Extended for WooCommerce (By StudioWombat)

Here you can test the long text field:
https://tiendahogardecristo.cl/producto/cojin-funebre/