install jupyterlab and jupyter-ai only and see if you still see this error. I see this error if installing both jupyter-ai and voila. So, there may be a version conflict in the dependency libraries, you can find it by installing your top-level libraries one at a time.
try to move this file “C:\Users<User Name>\AppData\Roaming\jupyter\jupyter_ai\config.json” elsewhere and restart jupyterlab, which will create a new config.json file. The config file saves the model selection and keys. When I did not set up my models and keys correctly, I saw this error.