With the new version of WooCommerce, it seems Variations doesn't work correctly for me.
I create my attributes and mark "Used for variations" and "Visible on the product page". Then I link all variations and add a default selection. After I save it and publish, it doesn't show on the product page, and both the check marks for "Used for variations" and "Visible on the product page" are gone.
If I change it and look again, it shows, but the price doesn't change. Also when I open that product again, sometimes the variations have been disconnected from their attribute.