Starting in Maya 2024, (I am writing this because it doesn't work for me in 2025), Maya no longer includes by default pymel, now is necesary to install it by yourself.
This is a tutorial step by step on how to install it, I tried the autodesk way that is described on the website and still didn't work, since at the moment the original luma pictures repo still doesn't offer support for maya 2025. So looking through the internet I found a way to install it from a fork to the Luma pictures repo, in order to do that you will need to install git first.
Go to the following page to install git Git - Downloads (git-scm.com)
Download the corresponding version and run the installer.
After this the git command should be something you can execute from the terminal.
You can test this by opening a terminal and running the git command.
To open the terminal just right click in your windows explorer inside a folder and chose the option open in terminal.
A new terminal should open, displaying the folder that you are located at as the root.
There you can test write the git command and hit enter, and you should get something like this.
After doing this, you can go to the maya install folder that for me is located on the path C:\Program Files\Autodesk\Maya2025\bin and there open a new terminal.
And run the following command.
./mayapy -m pip install git+https://github.com/iamsleepy/pymel.git@master
This will install pymel directly from a fork from a user that already added support for maya 2025.