It looks like this has been a problem for a LONG time. All the way back until the earliest versions of Unreal Engine. But if you modify a Skylight, sometimes it will stop working.
In any project I have, if I delete the skylight and then undo the delete, the skylight breaks.
Building lighting does not fix this problem. It does not matter if the light is moveable, stationary, or static. It’s all the same. No light whatsoever.