You are using staging server - a separate instance of the ESP Component Registry that allows you to try distribution tools and processes without affecting the real registry.
# Nanopb Protocol buffer library for embedded systems. --- **Important**: This component is uploaded to the ESP Component Registry unofficially and is not affiliated with the Nanopb project. It is used as a dependency of the [LiveKit ESP32 SDK](https://github.com/livekit/client-sdk-esp32) and may not be regularly updated with the upstream project.
idf.py add-dependency "ladvoc/nanopb^0.4.9"