Thanks again @centrobolsos
I'll have to experiment with this, as I noticed that (as a customer) there was no button for an "out of stock" item. It could be that I have customised the message when an item is out of stock (classic theme, prestashop v1.7.6.5). So I might remove the message, and see what happens.
Do you have a screenshot of an example of this button that's supposed to appear?
I hope they work on this module more as it would be great for a shop owner to know what customer want if the stock is depleted.
Again, thanks for your help, you've been amazing.