mm-music-player module: no volume-slider displayed

[kveel]

Hallo, I have installed the mm-music-player on my Magic Mirror and after adding “font-awesome.css” in getStyles (in mm-music-player.js) and unhiding the cursor the module works great!
However, for some reason, that I don’t understand, I do not succeed in getting the volume-slider displayed. If correctly, this slider is called by the jquery-ui.min script.
Can someone give me a hint, what could be the problem? Thanks.