When you click Add to Cart on the product list page or use “Custom Add to Cart” on the product detail page, there will be a prompt for variable products: **** option is mandatory, but in fact, it is already selected by default. When I use “Add Product to Cart”, the product can be added to cart normally.
Ok, but the button you add to cart is not the one I was referring to. I have removed the add to cart button I added after all considerations though. Hopefully next time the reply will be faster.