We've seen a few examples where a Raspberry Pi Pico suddenly stops working - the code stops running, LED stops lighting or the Pico shows no files in the directory once connected.
Luckily there's an easy fix for this!
At the bottom of the Raspberry Pi Pico Getting Started page, you will find some guidance on how to reset the flash memory, including a download button for a file to fix the issue.
It's a simple process - download the UF2 file then drag and drop this into your Pico file directly when in storage mode. This should reset your Pico and bring it back to life.
https://www.raspberrypi.org/documentation/pico/getting-started/