i have sorted the issue. I went through /admin/coupon.php again and discovered these two reference lines at the very top:
require('includes/application_top.php');
require( DIR_WS_FUNCTIONS.'coupons.php' );
Upon checking my /admin/includes/functions/ directory, somehow Ifailed to copy the 'coupons.php' file to that directory.Copying the 'coupons,php' to the /admin/functions/ directory, I can now open the Discount Coupons page and create a coupon.
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psseuro got a reaction from FirestormDOD in [Contribution] Discount Coupon Codes