I followed the directions for noise removal (select a few seconds of noise; then click Get Noise Removal). But absolutely nothing happens. I tried it with a couple different .wav files, but no response.
I experimented with other effects (echo; change of pitch) and they worked fine. But not noise removal.
Noise Removal is a 2 step process. First you need to capture a noise profile, then you need to run the effect a second time to remove the noise. See here for more detail: Audacity Manual
Either select the portion of the show you want to reduce, or select the whole show for the second pass.
You should describe what you’re trying to achieve. Noise Removal never does what anybody wants it to. It has a really good track record on that. Plus, it’s a two-pass tool and that loses many people.