I get the following when I try to upload to YouTube. If I try to export to computer elements splits my video into 2 files .aac the audio track and .m4v the video track neither of which I can play on the computer or upload to YouTube.
Unfortunatly there are times with direct upload to YouTube does not work. It may be a change in the protocols at YouTube or other internet anomolies. A more reliable workflow is to output a standard MP4 to your computer then, in a second step, upload that video using YouTubes dedicated uploader. A bonus is the opportunity to play and review your work before it goes live on YouTube.
Try using these settings to make your computer file.