Hi!
Cool, now follow the previous instructions that I have already told you:
Make sure to delete any file or directory related to fastapi and pydantic in these locations:

/usr/lib/python3/dist-packages
/usr/local/lib/python3.11/dist-packages

Then run:
pip3 install pydantic==1.10.6
pip3 install fastapi==0.74.1

Then the server should run as expected, I tested it and it worked.

Greetings!
Diego