Hi,
We got the URL with the first message. It was just a mistake in Philip's message.
Thanks for the screenshots.
The problem is this:
You've configured the cart module to be displayed with the "shop" menu item.
And on the shop menu item, it's actually a Joomla article page with a HikaShop content module displayed in it with a content tag.
With Joomla, the current menu item has to match with the component used to display the main area of the page.
So if you want to display a product details page, the current menu item needs to be of one of the types of menu items of HikaShop.
So the links of the products in the module there can't use the shop menu item.
That's why, when you click on a product of that module, you can see in the URL "component/hikashop". This happens when there is no menu item provided when generating the URL.
So, when you arrive on the product details page, there is no current menu item, and thus the cart module doesn't display.
To solve this situation, the HikaShop content modules have a setting "menu" where you can select a product listing menu item to be used for the links generated by the module. So edit your products listing module via the Joomla modules manager and select a products listing menu item in that setting. Then, the URLs of the products in that module won't have "component/hikashop" anymore in them, and instead, they'll have the alias of the menu item selected in that menu setting.
Then, in your cart module, also select this products listing menu item in the menu assignment so that the cart module can appear on the product details page.