Diagnosis
The activity zones or sensitivity settings are likely misconfigured. The passive infrared (PIR) sensor has a narrow field and needs clear line-of-sight.
How to Fix It
In the Arlo app, go to the camera's Settings > Motion Detection. First, set Sensitivity to Max. Then, draw an Activity Zone that covers the entire camera's view. Ensure "Record only activity in zones" is OFF.
If That Didn't Work
The PIR sensor needs a clear heat signature change. Ensure the camera isn't pointing at a heat source like a vent or window with sunlight. Relocate the camera so motion happens across its field of view, not directly toward it.
Heads Up
The Essential Indoor 2nd Gen does not have advanced AI person detection. It relies solely on basic PIR and pixel changes. Expect false negatives and positives.