Woocommerce product attributes

Hello,

having issue with woocommerce product attribute displaying. In admin backend product listing custom column i’m displaying product attributes – attached link of the screenshot.

But after updating product attributes – they’re missing in this column, but in frontend (in e-shop) and in product editing window – attributes are visible.

I checked database tables for these products – and attributes are empty there too. Where does WordPress store values of product attributes? And why they become empty after editing?

Thank you.

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