Viewport Shading option dropdown non-functional

I’m working on a model, currently with the skin modifier, and I have done something which has disable my ability to choose shading options from the Viewport Shading dropdown. In older saves of the same project it works but I honestly can’t tell what is different. At one point I changed the UI to get rid of the animation tools and I must have inadvertently changed some other setting as well.

The Z hotkey still functions as expected, thank goodness.

Thank you!