Why Does analogWrite Not Work on This Pin?

Short answer: analogWrite only works on PWM capable pins. Not every pin supports PWM.

How to check PWM pins

Arduino Uno PWM pins are marked with a tilde. Pins 3, 5, 6, 9, 10, 11.
Arduino Nano and Mega have different PWM pin sets.
ESP32 uses PWM on many pins, but you still need to configure it in code.

Common mistakes

Using a non PWM pin for analogWrite.
Forgetting to set the pin mode to OUTPUT.
On ESP32, using Arduino style analogWrite without the proper PWM setup.

Quick test

Move your wire to a known PWM pin and try again.

Bottom line

analogWrite only works on PWM pins. Check your board pinout and use the right pins.

Related: What is PWM and why is my LED flickering? · Do I need a resistor for my LED? · What is the difference between digital and analog pins?