Bang it at night or put a rare earth magnet around the housing til you hear a click. Those things might help a stuck IR filter if the lights turn on. If not, log into the camera's web controls and look around. You won't get advice on how to do that without knowing what camera you have. There's also the possibility that you got it free for a reason- it's broken. If so, then find a daytime only job for it or add lots of white light for night use. If the camera clicks afer it goes dark but you get no IR lights coming on, add an external IR illuminator because the IR ring is probably dead but the filter is still retracting.