fontsizeselect parameter not adding button in in tinyMCE

Here is my code that should add fontsizeselect to the menu:

tinymce.init({
            selector: '#mytextarea',
            plugins: 'lists',
            toolbar:
                "fontsizeselect undo redo | styleselect | bold italic |  outdent indent | numlist bullist",
            fontsize_formats: "8pt 10pt 12pt 14pt 18pt 24pt 36pt"
        });

However the fontsizeselect button does not appear.

From this article it gives this command to show all available buttons tinyMCE.activeEditor.ui.registry.getAll().buttons

However when I run it, the fontsizeselect parameter is not shown: screenshot of console

I created my app by installing from npm with npm install tinymce found here.

I can't figure out what I am missing. Are there other things I need to install? I have tried in FF and Chrome.

EDIT: My code works when I am using the cloud version of TinyMCE, but I want to use the local version.