Hey Frank,
Working now. Problem was that I was not using the incognito mode of the Browser. I could see the autooptimize.js file in the HTML source, but in the DevTools under Network tab I could not see the autoptimize.js file, but only a long list of other .js files. Using incognito mode, I can also see the autoptimize.js file in the Network tab now.
Thanks for the help.
