I hope that does the trick for you, but failing that, before contacting support, I would do a careful visual inspection of the camera, comparing it to a known good one. Maybe you can spot something from the front. Something near or over the lens, or something out of alignment inside, just behind the front glass. Should be easy to spot if doing a comparison.
Then again, you did say it was fine during the day, so this does seem odd. See if the IR LED looks to be mounted correctly.
Here’s a thought, try turning off the IR illuminator, in the settings, and use the IR illuminator from the known good camera to light the scene. See if you get a picture then. If you do, then you know it’s something to do with the camera’s IR illuminator, or the IR filter getting stuck.