Hi,
The path seems wrong from a long time. I can't find any "okpay asset" in HikaShop.
The plugin has been developed by "DigitalArtJoomla", I guess that when we received the plugin source to integrate it, the assets where missing or we didn't add it without modify the "end" view.
I fixed the view (by removing the complete CSS for the button), it will be include in the next package.
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.