Jupyternaut (jupyter-ai) in Sagemaker Studio notebook. How to get it working?

I'm using a jupyterlab notebook in Sagemaker Studio. It's Jupyterlab 4.0.8, running a Python 3 kernel. I've selected an AI21 :: j1-large Langage mode and an OpenAI :: text-embedding-ada-002 Embedding model. (I'm not familiar with the strengths and weaknesses of the models, so my choices are pretty much random.) I got API keys from AI21 and OpenAI and entered them into the interface. But jupyternaut is unresponsive. It just doesn't answer anything I put in the chat prompt. I did pip install jupyter-ai in the aws cloudshell cli. It installed successfully. I also did pip install jupyter-ai in the sagemaker notebook. Requirements were already satisfied. Still no response from jupyternaut. I also tried the %%ai magic. I got UsageError: Cell magic %%ai not found. Can anyone help me get the ai chat working?