Suddenly can't select multiple objects in 3D view

The cat walked across my keyboard. I don’t know what he pressed, but now I can’t select multiple objects. It’s as if my shift button just stopped working, but only for that. I can still select multiple vertices, etc in edit more and I can still use it to navigate around the space.

Any Idea what the fuzzy little twerp may have done?

Blender 2.93.5

If you start a new file, did the problem persists?

Good question. Nope. And by closing my file and opening it again, that seems to have resolved it!