A very common problem, but a very uncommon cause. I’ve gone through dozens of threads like this one and people always insist that it’s in pause mode or there is nothing selected, but that is absolutely not the case for me, Audacity just insists on keeping everything greyed out for no discernable reason. I’ve tried re-installing everything, it does nothing.
That’s not labeled audio. That’s selected audio. Labeled audio has a label track.