Variation Products in my woocommerce do not add to cart

I have a store with the Urami WP Theme and it worked perfectly but now. All the variables are shown on the product page, but when I select a color and or size and then want to add this product to my cart, it does not work. If I change it into a simple product the add to cart button works fine and I am redirected to the page for payment as it should. What am I doing wrong on the variables? I have checked out different tutorial videos to check, but I cannot find it.