Hello,
I checked your child theme and the code is there https://prnt.sc/1vp8drl
But you disabled the Buy now button in the product settings https://prnt.sc/1vp8fhp + I added the below custom CSS https://prnt.sc/1vp8kra
Check now.
You can enable percentage discount in the Theme Options > WooCommerce > Shop elements > Sale and Out off stock > https://prnt.sc/1vp8x6k If you want to place it directly like on the screenshot it requires additional customization. You can submit customization request here because additional customization is not included in theme support https://themeforest.net/page/item_support_policy .
Regards