Hi! This error typically measns that there's already something else running on localhost:8080 – maybe your Jupyter notebook, maybe an old Prodigy server, maybe something else.
If you don't know what it is, you can try find it and kill the process (see here for how to do it, depending on your operating system). Alternatively, you can also run Prodigy on a different port that's free, by setting the environment variable PRODIGY_PORT, for instance PRODIGY_PORT=9000 (there's also a magic command for setting env variables in notebooks).