server connection error when launched by anaconda or opened in terminal.

This has happened when reinstalling the newer version Anaconda, The specific error is Server Connection Error and port 8888 is used, Invalid response: 500 Internal Server Error.

No file, test, or entry point is named. Start by reproducing the launch through Anaconda and from a terminal, using port 8888, then inspect the server connection failure and its 500 response. Done means identifying the cause of the connection error and documenting or fixing a reproducible resolution.

Written by the indexing model from the issue text.