In the readme, it says use Firmware esp8266-20170108-v1.8.7.bin. volume.py uses led_v.on() which requires at least MicroPython v1.10. I know it works with esp8266-20191220-v1.12.bin, but maybe you want to update the readme to the version you're using.
In the readme, it says use Firmware
esp8266-20170108-v1.8.7.bin.volume.pyusesled_v.on()which requires at least MicroPython v1.10. I know it works withesp8266-20191220-v1.12.bin, but maybe you want to update the readme to the version you're using.