Hello, Gewoonbovenaan,
We have outlined what exactly and which plugin is causing. In fact, it will only work properly if both plugins are disabled https://prnt.sc/e786umtNmDrq One of them causes Ajax adding to be disabled even from the shop, while the other simply throws an error when clicking on “Add all products to cart”.
Our devs will check if there is anything from our side that can be done to help you and we will give you an answer within a few days.
Kind Regards,
8theme team