Youtube
I don't know exactly what's up, but whenever I try to post a score onto YouTube I do not get an E-mail verifying that my video is done, nor does a video even seem to be in the process of creation. Just recently I sent my score "Air and Dance of the Bells" with an MP3 file, and i haven't gotten an email telling me the software was unable to create a video, nor was a video made.
Comments
See: https://musescore.org/en/node/269690
HTH
Ypon checking your account, we noticed indeed that the videos are failing to upload to YouTube. Could you try to disconnect your YouTube account from MuseScore by going to "Send to YouTube" (from any score) and next click the disconnect link? Next, try to "Send to YouTube" again as it will try to connect your YouTube account again, so basically a fresh start. Keep us posted.