Pls kindly note that if there is no PIR detection, the camera will be in standby mode for saving power, once there are any PIR activities, the camera needs time to activate itself, upload the data to the server, and download that data to your cellphone.
Generally speaking, there will be a 3-6s delay, when the motion is too fast or short, your camera might not have a chance to capture it, appreciate your understanding.
If the Wi-Fi signal is weak, your camera will take a much longer time to be activated and upload/download the data to the server, pls ensure your camera is connected with a strong and stable Wi-Fi signal.