There is no way that the button is not displayed by HikaShop. Either the button's code
echo $this->cart->displayButton(JText::_('OK'),'ok',$this->params,hikashop_completeLink('address&task=save'),'if(hikashopCheckChangeForm(\'address\',\'hikashop_address_form\')) document.forms[\'hikashop_address_form\'].submit(); return false;');
has been removed in the file "form" of the view "address" via the menu Display>Views, or the code around altered, or the cart helper's displayButton function has been modified, or there is a system plugin which removes the HTML of the button on your website.