If I view the page on Amazon.es for the rice, I see:
Agotado temporalmente.
Estamos trabajando para volver a tenerlo en stock lo antes posible.
Enviar a Canadá
As you may be able to guess, I am in Canada. The servers for meta are located in the US. I suspect Amazon is also telling US visitors (including the Onebox bot) that the product is unavailable.
Ultimately we can only generate a response based on what Amazon tells us.
Here is a product that Amazon.es is willing to ship outside of Spain, and therefore includes a price which Onebox can detect and display: