Hi,
Thanks for the access. I found the issue.
It comes from a lack of backward compatibility with some menu items in the integration with the language switcher module.
Would you have deleted your menu items and recreated them with the same options selected, you would not have had the problem.
I've added a small patch so that it can work even without this, as it is to be expected.
It's now working fine on your website as far as I can see.
The fix is quite easy to add for anyone interested. You just need to add the code:
if(empty($p->selectparentlisting) && !empty($p->category))
$p->selectparentlisting = $p->category;
before the line:
if(empty($p->selectparentlisting) || $p->selectparentlisting != $cid) {
in the file components/com_hikashop/helpers/association.php
We'll add that to the next version of HikaShop too.