Which specific YouTube add-on are you using, and which version?
The main YouTube add-on in the official repo is currently out of date, as its original author has stepped away from supporting it. There is however a newer version available for install via zip file, and hopefully shortly via a repo too. See
this thread for more details and a download link.
Or if it's one of the other YouTube related add-ons, please let us know which one so we can be more specific.
But to your original question, YouTube works fine on all my Jarvis installs using the add-on linked above.