Hi,
Can you check the settings under the Checkout tab of the HikaShop configuration page ?
There, in the "Cart" view, you have a setting "read only". If that setting is activated, the quantity input will be removed from the cart display and you'll only see the quantity as a text that you can't change.
The look of what I see on your checkout is precisely what you would get wen that setting is activated.
So please check if that's the case, and if so, please turn it off and it should display like you want.