Motion Detect only at night

[Striker]

I have two IP3M-943 cameras. On motion detect, they only seem to work at night. It snowed hard last night and I was getting emails and alerts pretty regularly. Now today I'm out in the driveway clearing snow and brushing the car off and no alerts. I don't get it. Is there a setting I'm missing? I have the schedule set for 24 hrs because I'm away a lot. Should I increase the sensitivity more? They detect snow so I don't want to go too high? Thanks,

[Striker]

I figured out how to fix this but I don't understand why. IF I set the threshold over 5 and the sensitivity under 85 my motion detect won't work in the day time. Doesn't make any sense to me unless the signal from the camera is too low. Anyone else know why this would happen? Thanks,