Simple products not added to cart

Hi,

I’ve installed PPOM but it seems not working in simple products.

For example in this one, I can’t add to cart the product:

https://watequeshop.com/item/cepillo-bebe-personalizado/

And for the same meta group in a variable product, it works:

https://watequeshop.com/item/bandeja-navidad-personalizada/

The page I need help with: [log in to see the link]