Same here with latest Woocommerce (2.X) and WordPress and 1.6.0.2 of this plugin. Luckily our automated tests noticed it. I debugged it for a while in the IDE but couldn’t pin point the error.
It doesn’t work with “Once when invoice is created/emailed” but seems to work at least in My account with “only for specific order statuses”. I’m also not seeing the link anymore on the “Order confirmation” page and neither in “My-Account” so presume it is also related to email attachments.
