Flatter child coupon theme doesn't show the coupon code box

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Hi, I am using the Flatter child coupon theme for my site https://www.quponify.in

The site was working fine till yesterday and started creating problems today. The “Show coupon” button doesn’t show the coupon code box which contains the coupon code.

Please help me out in resolving this issue.

PS: I am not very good with coding.

Thanks