The reason you were unable to get the onboard neopixel to operate was most likely you did not enable power to it via GPIO10 first. This is done on a lot of boards in order to enable low power operation. Its clear if you look at the schematic.
I decided to write this tutorial because the manufacturer’s website contains some errors regarding the use of this board with Circuitpython. Although the site contains the information that the firmware for the board is the same as that of the Raspberry Pi Pico, I noticed that some features were not present. Especially when we use the expansion board. The examples on the Seeed Wiki are mostly suitable for use with the Arduino IDE. But the examples for Circuitpython are not well documented.