All Image Effects automatically disabled

Absolutely none of the standard assets image effects work, and all cannot be enabled.

What stupid thing am I not doing?

What version of Unity are you using?
By “standard assets image effects,” do you mean the effects obtained via the “Effects” package from the add asset menu? If so, may want to try the Post-Processing Stack instead: https://www.assetstore.unity3d.com/en/#!/content/83912