Error on Link all variations

Hi,
I created a product with some attributes and variations. I checked attributes with “use in variations”. I saved product as draft (I hope this is the right translation from italian “Bozza”).

Then I clicked on “link all variations” button in variations tab but I received a message that says “no variations added”.

I tryed with site online and old local version, but I have always the same problem.

Some days ago I update WordPress on 3.9.1 and WooCommerce plugin on 2.1.9. Before of this all works fine.

I tryed to deactivate all plugins (except WooCommerce, of course) and change theme to the classic “Twenty…” but “link all variations” button still not working.

Finally I indicate that creation of variations in manually mode works fine.

Ideas? Thanks.
Alessio

ps. sorry for my english

https://ww.wp.xz.cn/plugins/woocommerce/