I've been working on a building based mod for weeks, no problems so far, everything is going fine. The lighting is also going fine. Then today, no matter what I do the light bulbs will not show up anymore. If I drag a light on to something it still lights up, but I cannot select edit edit the scale of or move the light like I used to be able to, and the light bulb symbol doesn't show up at all. I did a search on creation kit keyboard shortcuts, and none of the lighting based keybindings here helped either.

Any idea what's going on?

Ctrl+i

That toggles light markers on and off. You need to have markers on to see them though. Toggle that with M.

You haven't got markers disabled by any chance? M for general and Ctrl + I for lights.

If you haven't delete your INI files and re-generate them.

Thanks you just saved me minutes/hours of frustration.