All products show in every category

Hi,

Please try to add the line:
$params->set('content_synchronize', 1);
after the line:
$main_div_name = 'hikashop_category_information_module_'.$params->get('id');
in the file "listing" of the view "category" via the menu Display>Views.
That should fix the problem (it did when I reproduced the problem on my end.

Hi,

I don't see why it wouldn't work.
Download again the install package on our website and install it on yours.
That will add the patch and it should hopefully works.
Also, make sure that you clear the cache of your website if activated via System>Clear cache in your Joomla backend.
If that still doesn't work, we would need a backend access to check things out.