It sounds like your cameras are placed in the window. They will work fine during the day, but the reflection from the window will cause a blur at night. Try moving the cameras outside or away from the windows to get rid of the blur.
You may have done what I did, and I kept getting an invalid registration error. You have enter the name and registration number from the back of the unit. I was entering MY name. Don't enter YOUR name. You have to enter the name on the back of the unit, along with the reg. number.
