Hello,
How that coupon is created ?
When you want to have a discount or a coupon which will be applied to vendors, you need to configure it via the HikaShop backend.
Otherwise, HikaMarket will consider that the coupon is only a deal between the store and the customer and won't affect the vendor for it (like a "credit" coupon create by the store for a refunded order).
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.