Just on a side note: I went ahead and tested the direct interfacing and uploading to YouTube in the most current version of Music Maker (27.x), and it works for me. So, you might want to consider using your option to upgrade to the current generation free of charge. You can download and install the current version from this link:
After this is done, enter the old version's serial number into the "Activate Edition" dialogue to unlock the feature set and instruments associated with your old version. These will then be gifted to your in-app store account, and thus become available to you in the new version.
PLEASE NOTE: The YouTube sharing option will only be available if you actually have any image/video material in your project, as YouTube will only accept video files. If you're working on a purely musical project in Music Maker, the YouTube option will be greyed out. Audio files are not supported for upload to this platform.