Hi,
There are several things to do.
First, you say that the problem is only with some orders.
Do you have several payment methods and the issue only happens for one payment method ? Which one ?
Also, the order not being confirmed means that the payment plugin didn't receive the payment notification from the payment gateway or received it and couldn't process it.
We actually have a documentation about this for PayPal here:
www.hikashop.com/support/documentation/i...or.html#notification
Most of the points there should apply for any payment method. So I would recommend reviewing them.
One thing recommended there is to activate the "debug" setting of the payment method and try again. That way, it will fill the "payment log file" available in the HikaShop configuration with information about the issue.
So I would recommend checking that out.
Finally, most payment gateways have information about failed payment notifications in the merchant account interface they provide to the merchant. So it's also interesting to check what information can be retrieved from there.