Camera is detecting everyone except one person

So we recently start es renting a room downstairs and the new person uses our driveway it's visible in the doorbell camera, but two weeks after he moved in it started to not detect him or his car parking at all. The camera even detects movement farther from where he is parked but won't detect him walking on our sidewalk or his car. Is there a way for him to block the camera from seeing him or could there be a way that he hacked it? It's just very weird that it detects everyone except him and his car