Regarding zencart order not show in zencart admin, due to zencart architecture where it only create order when it get payment status from payment gateway.
But event such as mention in (a) , (b) and (c) then no order created in zencart.

 

It possible that
a) customer accidentally close web browser thus iPay88 not able return status to zencart, or
b) customer internet connection drop/timeout thus iPay88 not able return status to zencart, or
c) customer computer hang and the connection stop thus iPay88 not able return status to zencart.

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