latex newcommand macro not working

[dealmeidavf]

Hello,
This does not work on Jupyter Notebook 7:

$\newcommand{\gradx}{\nabla}$
$\gradx$

not even on the same markdown cell. The error is: undefined control sequence \gradx
Does anyone have LaTeX newcommand working with Jupyter Notebook 7?
Thank you.

PS: systems:

1. MS Windows 10, conda fully updated, Notebook 7.3.2, Edge
2. Gentoo Linux, python environment (pip install of various packages), Firefox 128.9
3. The above commands do work using Binder: JupyterLab 4 + Notebook 7 + NBClassic on Binder. I have tried the same requirements.txt installation files but no luck on 1, 2, above. Any insights on what I am missing in my systems? Configuration? Missing package? Enabling extensions? Thanks.