Hi,
It could be a bug of HikaShop 5.0.2. Also, are you using the multicoupon plugin for HikaShop (
www.hikashop.com/marketplace/product/164...coupon-checkout.html
) ? Old versions of the plugin had several bugs in it so it could be linked to that.
I would recommend updating to the latest version in order to make sure you have all the patchs. Then, try again. If you still have the problem, please provide information to reproduce the issue on your website and a backend access and a FTP access via our contact form so that we can look into it.