Have you read the FAQs here in the support section about best camera positioning as well as changing motion sensitivity in your modes and rules? How far away is the subject you're trying to capture? Remember that the PIR sensors only capture people out to maybe 25 feet, depending on these variables and others.
welcome to Arlo. I've had people come down my back walk into the house get something and leave. Same exact path but nothing on them coming in but catches them leaving. Had the mail truck pull up drop off a pkg. and leave. Nothing on them coming but catches them half way back to the truck. Not always the case of course but not a good thing when it does.
add that this evening I went out my backdoor walked to the garage and turned off the water turned and walked back to the house clearly in the video for 48 sec's and didn't get a notification because it called me a motion. Makes me feel safe. I'm 71, I don't move fast enough to be mistaken for motion.