Below are the steps to follow when Gulp no longer works post-upgrade (or for other reasons).
Install NPM again from the terminal and check if you can run the gulp task
If still does not work, then run
npm audit fix
npm audit fix --force
After this, you should be able to run Gulp, but it still will not work.
Finally, you will need to delete these 2 files in the highlighted location
Then run Gulp again and it should all work! (Make sure to clear cache!)