When a reading is wrong

Six symptoms

Pick what the reading is doing. The ringed part of the board is where to look first, and the list beside it is the order to check in, by how often each one is the answer.

It reads 0, or it is stuck at the top

A reading that sits at 0 and never moves means SIGNAL is not being pulled up: VCC is missing, or the cable is one pin over. A reading stuck at the top of the scale means the transistor is passing no current, and the usual reason is a missing GND. Count from the square pad: GND, VCC, NC, SIGNAL.

It rests nowhere near half the scale

That is how this block is built. The resting level is set by the gain of the transistor, which varies from part to part, so from 5V on an Uno it can be anywhere from about 325 to 815. The resting level works it out. The sketches measure it rather than assume it.

Talking does nothing

Also how it is built. Speech a metre away swings SIGNAL by a few millivolts, a few counts on an Uno and inside an ESP32's own wander. Clap a hand's length away: if the swing jumps by hundreds of millivolts, the block works.

It jumps with no sound, or one clap switches twice

Readings that wander in silence are the converter's own noise, which is larger on an ESP32. Measure the quiet swing at start-up and put the threshold above it, as reading it on an ESP32 does. A clap that switches twice is its own ringing and echo landing in the next window: stop listening for 300 ms after each switch, as a clap switch does.