Why is my product written as out of stock ?

Hello,

I have a variable WooCommerce product here :
http://www.lefournilbriard.fr/produit/eclair/
It's working well

And another one here :
http://www.lefournilbriard.fr/produit/sandwichs/
This one is always written "Out of stock", I cant find why ...

Do you know why ?
Many thanks in advance
Kind regards