Is the order status confirmed ? If not it means that the payment notification from the payment gateway was not received by HikaShop:
www.hikashop.com/en/support/documentatio...or.html#notification
Also please check that the hikashop group plugin is published and that its access level is public.
Finally, if you're using a payment method were the payment happens on your website during the checkout, you should try to add the code:
function onAfterOrderCreate( &$order,&$send_email){
return $this->onAfterOrderUpdate( $order,$send_email);
}
before the line:
function onAfterOrderUpdate(&$order,&$send_email){
in the file plugins/hikashop/group/group.php