Blender 2.81, Why are my Light and other settings GONE? I have literally no light settings available.  I have the same problem with material settings.  Almost all of my material settings are gone also. It works fine on an older saved file.  Also works fine if I create a new file.  All light sources in this scene display ZERO settings such as color, power, radius. :(

What did I do to make them disappear? I have tried everything and searched to no avail.  Unfortunately, none of the suggestions has fixed it so far.

I have also downloaded and reinstalled 2.81 with no difference.
That happens when you have hidden "layers" in an old version of Blender and open it with 2.8x. To show the items click the tv and camera-icons to make everything visible again. 

See the second image, click the tv-screen and everything is visible again.