I can’t "add to cart"

on kiabi site.

I've had this problem for a month or two. On other clothing sites I can order, but on this one it works differently—even though before there were no problems.

I can choose the garment, the color, the size, but as soon as I click "add to cart," nothing happens.

I've tried changing my proxy, but then it doesn't display the sizes, so when I click "add to cart," it tells me to first choose a size, something I can't do since they don't appear!!!

I also had the chance in the meantime to change my hard drive, and nothing changes.

Does anyone have an idea?

Thanks in advance.