jupyterlab installation instructions do not work

[buffetboy2001]

In the README, we have this recommendation for installing to use with JupyterLab:

jupyter labextension install ipysplitpanes

But when I use that, I get:

An error occured.
ValueError: "ipysplitpanes" is not a valid npm package

I have the following software stack:
jupyter core : 4.7.1
jupyter-notebook : 6.2.0
qtconsole : not installed
ipython : 7.21.0
ipykernel : 5.5.0
jupyter client : 6.1.12
jupyter lab : 3.0.11
nbconvert : 6.0.7
ipywidgets : 7.6.3
nbformat : 5.1.2
traitlets : 5.0.5

Any recommendations on how to get passed this? Thanks!