Thanks for testing out Prodigy. I'm sorry you're having issues. Hopefully we can find some resolution.
Unfortunately there could be many possible issues.
What is your intended goal with multiple instances? Are you trying to have multiple users annotate the same data/task simultaneously? If so, are you aware of multi-user sessions? This is typically recommended if you have multi-users annotate the same data/task.
What is your strategy on setting ports? Have you only used the default or have you modified ports?
Do you have the same issues if you run commands through a terminal (instead of Jupyter)?
From this post, it seems like you may be trying to run multiple instances on the same port. This could explain why you're seeing a different instance.
Related, here's another relevant post.
This first one suggests a few options that has worked for others:
Trying a different port
Reinstalling the murmurhash package
Issues with how Jupyter / JupyterLab is handling the server. See link below for help.
Let me know if this helps or if you're able to figure out any further issues.