Product availability value don't change when choosing different Combination

[grazdemaio]

Hallo I'm going crazy with this issue, of course I carefully searched on the web and in this forum but I can't find a solution.

I have pruduct with combination and different quantities for each combination

In the frontend>product page if I change the combination, the available quantitiy does not change/update.

Here one of my product page http://dottorbike.it/shop/abbigliamento/175-353-maglia-scott-endurance-as-ssl#

Size M has 1 peace and size L has 2 peace. But when you select the quantities is not changing.

In this Prestahop this features is working right https://procyclingpoint.com/it/la-vuelta-2017/3534-maglia-angliru-el-infierno-santini-la-vuelta-2017.html#/

 

Can please someone help me or put me on the right path?

Thanks in advance

Graziano