Hi,
You need to edit your custom field in the HikaShop backend and configure the "display" of your fields to let be visible (and so editable) in the front-end edition page.
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.