Hi,
The issue is that your turned on the "use bootstrap design" option of the HikaShop configuration but your template doesn't fully support bootstrap (the CSS of bootstrap is loaded on your pages but not the JS of bootstrap). And thus the javascript handling the openning/closing of the accordion system is missing.
I see three solutions:
1. You turn off the "use bootstrap design" option in the HikaShop configuration.
2. You ask your template provider for help with bootstrap not being fully loaded. Maybe there is an option to activate or something to add the JS of bootstrap in the template settings...
3. You edit the file "listing_list" of the view "category" via the menu Display>Views of HikaShop and add the line :
$this->tabs->mode = 'bootstrap';
after the line:
$this->tabs = hikashop_get('helper.sliders');
in order to force the use of the mootools accordion system instead of bootstrap's and hopefully that will be enough to circumvent the issue.