Problem with adding font-awesome to app

Hi guys

I want to add fontawesome to our app, like described here: https://mxforum.mendix.com/questions/18142/Adding-glypicons-to-Mendix-Modeler.

What I did was:

1 - downloaded v.4.6.3 and copied the font folder of font-awesome to the theme folder.

2 - I pasted the classes into the custom.css and custom_variables.scss

3 - give the button the class name

4 - zipped the theme to a package

Now it should work I thought, but no... But I even dont see that the classes are read...what do I mis?