Size attribute is not showing on front end of woocommerce site

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PHP

WordPress

i have a woocommerce website. Options for size attribute is not showing on the front end of my website although the size attribute and options are present on the back end. Check the product below. http://nervesdeals.com/product/band-detail-mint-green-blouse/

What I have tried:

I tried disabling my optimizations plugins but it didn't work. I got a solution which is to remove the size attribute and adding it again. this is working but it requires lot of rework so i am want to know why this problem is occurring and is there a better solution than the current solution i have.