Hi,
It is possible that you have some CSS override for the HikaShop backend CSS file.
Please edit your HikaShop configuration in order to use the default HikaShop backend CSS file ; there you will have the new product edition interface.
Afterwards, you could see to re-integrate your backend CSS modifications into a new override, based on the latest HikaShop CSS file.
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.