Hello,
You have to add that user to your main vendor.
In the HikaMarket configuration, in the "your vendor" tab you will find the "users" section just like when you edit one vendor.
The "Your vendor" is also call the "main vendor", it has the same access that you have in the backend, but in the front-end and with all the ACL features provided by HikaMarket.
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.