Hmm, are you using the latest examples? I think import picodisplay kind of retired when the whole PicoGraphics thing happened, so it might be you’re trying to run older code on newer firmware?
(i.e. the latest https://github.com/pimoroni/pimoroni-pico/blob/main/micropython/examples/pico_display/balls_demo.py imports picographics, not picodisplay)