Alert button don’t show on archive pages for variable products

Hi,

I’ve been using this plugin for a while and it works great.
But for a few weeks (months?),the “Alert” button hasn’t been displayed for variable products on category archive pages.
It works perfectly on product page, including variable products ; and it works on category archive pages but only for simple product.
The option “Show on Archive/Shop” is well checked in the settings.
It tried to deactivate all plugins but nothing changed.
Any idea what the problem could be ?
Thx !