Add Product Goes Dim

I have two sites with the same problem. When a customer tries to add a product to the cart, the page goes dim and remains that way. I have deactivated all my plugins and tried it and it does not work. I have tried a twenty sixteen theme with no change. I upgraded to wordpress 4.6 – no help.All of my plugins have been updated. I am using Woocommerce 2.6.4 Can anyone help me with this problem? I think it happened after updating Woocommerce but I am not sure