Whole skybox went black

First off, the reason I'm not putting this in "Graphics" is because this is happening to every single skybox I try to use, even the default one.

I have no idea when this happened, as I've been testing stuff to improve performance and I never really looked up (especially since I had a fast day/night cycle). I noticed this when everything was lit up, and I saw from the corner of my eye, that the sky was pitch black. I went from the game view into the scene editor, and the entire skybox was black. I tried changing it from what I had been using, to the default one, but it's still pitch black.

This is a completely new scene I just created, for seeing if it was a problem with something in my scene. Apparently not.

Does anyone have any idea what to do?
Also, not that it matters, but I was using A.C's "Time Of Day System" skybox.

 

Bump.

I tried doing some more stuff like changing settings in the "Lighting" window, but still can't get it fixed.

There must be something obvious. This can't be the first time this type of thing happened in Unity.

 

*continues jazz hands, and psychopathic murderer smile face*

So, for some f****** reason. And don't ask me why, because I don't f****** know! The exposure on every since skybox material was automatically getting set to 0.

*flips out in time and space, and returns to do a Jackie Chan "WTF?!" meme face*

 

We are having the same problem, it's insane. Everytime I start up Unity I have to switch to another Skybox shader cause the currently used ones all went black... And next time I start up the new ones broke down and I have to switch back to the previous ones that miraculously work again.

 

Already two years ago...
Anyway, in case anyone like me still searching around in panic...

I finally find my solution.
Try switching the shader Cull mode to Off, not Front or Back. This just worked for me.

I encountered the same problem today when I was making a procedural skybox with ASE. The shader fully worked in Editor, but in actual Camera rendering(Game window, play mode and Build) it remained black if camera are still, also it behaved glitching, such as if you constantly move camera, it will works shortly but make camera Don't Clear at random period.
I have tried shifting the Queue and the RenderType, changing the Fallback shader , even changing the whole shader type template, none of them are working.

Anyway the whole thing is just weird because this procedural skybox shader was just working fine in my other project (with same unity version 2017.2f3), if i grab another similar skybox shader from the previous project to my current one, it failed again. I would rather consider this is a bug of unity.

 

This happened for no apparent reason in one of my scenes (luckily it was test chamber so didn't matter but still wanted to know why)

Some plugin had added another directional light, I had assigned the first one into Lighting settings sun source and switched the x-degree to "night" and the second one's x-degree into "day".

Luckily I got custom skybox with moon atop at night so I quickly realized it's not black bcz something is broken: it's just night!

So! Because I forgot about the first dir. light and started using the second wondering why the sky stays pitch black despite how I rotate the second dir.light.

TL;DR; 2 directional lights in scene and the wrong one in the "sun source".