A:Answer Hello,
The nature of PIR sensors is that they detect warm moving objects. Given that glass is quite a good insulator, it actively blocks this heat from the camera's PIR sensor and so the sensor cannot detect motion even though you can see movement happening. The IR lights on the front of the camera reflect back at the lens when behind glass and make it very difficult to see what is happening outside a window.
If needed, the IR lights can be disabled.
Please let us know how we may further assist you,
Thank you.
JV
Swann Customer Support