USB ISO URB sucess complation after send but did't send to device

My usb driver send out ISO urb pakages to device.Some times it will complation (sucess 0 bytes) very short time about 5us, it will not send to device, so my device can't get the data.
The flag is ASAP. the startframe right or wrong every time is not same.
Do you knonw what is happen?