Variable Product Does not work properly

I have designed website in storefront, all was going good but now all of a sudden the Variable Product does not work

If I go to Product Data – Attributes – Select Custom Product Attribute and click on ADD, it does not move further, (it was working earlier and now it does not)

My hosting is with Hostgator

Need help to rectify the same

The page I need help with: [log in to see the link]