Hi,
Regarding the error in the popup, I don't think it comes from HikaShop.
Edit the file libraries/joomla/database/exception/executing.php and change the line :
parent::__construct($message, $code, $previous);
by:
parent::__construct($message.' '.$query, $code, $previous);
And you'll get the full MySQL query in the error message.
Also, activate the "debug mode" and "error reporting" settings of the Joomla configuration and that way, when you get that error, it should provide more information on where that MySQL query error comes from.
Regarding the email:
HikaShop actually sends two emails by default, the order creation notification and the order status notification.
If the order is directly created with the order status "confirmed", then it's possible that only the order creation notification email is sent.
But usually, the order is first created, the email order creation notification is sent, and then the order is confirmed and the email order status notification is sent.
So I don't see why you would get only the created one besides that.
It might be related to the payment method you're using or how you configured it.