Likely causes
- Camera mounted behind a window causing IR reflection
- IR LEDs disabled in the app or on a schedule
- Dust, cobwebs or water on the lens or IR ring
- Nearby light source defeating the day/night threshold
- Hardware fault in the IR cut filter after long use
Quick checks
- Check the night vision setting in the app
- Clean the lens and the ring of IR LEDs
- Look for a bright spot or halo in the image
- Test with the room in complete darkness
Step-by-step fix
Clean the lens and IR ring with a dry microfibre cloth
Set night vision to auto in the app
Remove the camera from behind glass if a halo appears
Adjust nearby lights so the camera is not fooled into day mode
If the image stays colour in darkness, the IR cut filter is likely faulty