I was struggling with this problem for so long and it seems we are the only ones having this issue.
What ended up working for me was pip installing virtualenv and then creating a virtual python enviornment with 'virtualenv tmpenv' .
Next I coppied the contents of tmpenv over to AppData\Roaming\MathWorks\MATLAB\R2021a\ros1\win64\venv\
I had to create this outside of \venv\ because of the way the createOrGetLocalPython.m script works. There is a command to create the directory win64/venv/temp that will error out if the parent folders already exist.
I beleive the culprit is line 135 in createOrGetLocalPython.m:
[stat, res] = system(['"' pyexec '" ' fullfile(tempPythonExtractDir,'virtualenv-16.6.1','virtualenv.py') ' --no-setuptools --no-pip --no-wheel ' pyenvDir ' --system-site-packages']);
This line should setup the env for us, but in my case it was returning success but not actually creating it.
Hope this helps!