Hi @Sperkmandl, the skull app is still available on our Gallery, it is called Cyber Science - Motion and can be downloaded from here. Please be aware that this only works with our older V2 hand tracking software and you will need to apply this manual hotfix to resolve a compatibility issue with Windows 10.
From your description it sounds like you are currently running our new Gemini V5 hand tracking software. Please can you email me at firstname.lastname@example.org with the PC Spec (inc CPU), specific software version (About tab in the control panel will show this) and the tracker log which can be found at the location below and I will be able to check this for you to see why the tracking service is not running:
Please can you also check that you have no previous versions of our hand tracking software installed and running at the same time as this will cause conflicts.