Hi,
Your template is including jquery but jquery is already loaded by Joomla.
The effect is that the modules loaded for jQuery (like the modal.js file) are not available anymore, the template inclusion of jQuery erase the previous loaded one and all of his modules.
That's why you can see the input box for the upload below the upload zone.
So you can see to this your template jquery inclusion or you can change the modal system used by HikaShop.
In your HikaShop configuration, under the tab "display" you have an option called "popup mode".
You have to select "mootools" in order to use the bootstrap 3 modal, which use jQuery and the modal.js module.
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.