Bopo – WooCommerce Product Bundle Builder – I can’t add the bundle to cart

Hello,
I have a problem with your awesome plugin.

As you can see in this product:
https://www.bellantonicioccolato.it/prodotto/dragees-allarachide-e-caramello-salato-copia/

If you try to add two products to the bundle and then you try to add to the cart, this message error appear:
Bundled products is unavailable. Please select all bundle items before add to cart.
Why? Can you help me?

Thank you