Hi,
So if I understand, the problem is that you don't see the products listing when you click on a category, right ?
In that case, it could well be a problem with the template.
Try to temporarily switch to the default joomla template. If it displays fine, then it will confirms that.
In that case, try renaming the file templates/YOUR_TEMPLATE/html/com_hikashop/category/listing.php to something else via FTP in order to deactivate the view override on the display of the listing and that should hopefully fix the problem.