React Calculator won't display any input

I’m part-way through making a calculator with React and cannot get any of the inputs (be it numbers, operators, or the final result) to display. I’ve gone over the code many times, and my handleClick function looks to have been coded properly, but I can’t figure out where the issue lies. I’d really appreciate it if someone could take a look at my codepen and let me know what I’m missing.


The calculator logic isn’t fully complete yet because I’m focused first on getting the buttons to display.