At present, our Nimbus Course Builder does not support YouTube, hence this option has been grayed out and disabled from the Course Builder. The reason that this is happening is because YouTube will no longer be providing the bit of code which lets us use their videos in our courses (i.e. the ActionScript 2.0 Player API - https://developers.google.com/youtube/flash_api_reference_as2) if you are technical.
Our technical programmers have been working on an upgrade to the Course Builder to allow for HTML 5 delivery which would also allow for the continued use of YouTube but unfortunately we haven’t been able to achieve this as yet. This work will be done so therefore this function will return and this is only a temporary situation. As an alternative, please use hyperlinks. The clickable shape or text field can be created and the hyperlink to the YouTube file added as shown below: