What version of Premiere Elements are you using and on what computer operating system is it running?
I do not like to use the words never and impossible, but, when it comes to uploading a 21 minutes long Premiere Elements Timeline to YouTube via its YouTube feature, it is impossible to upload more than 10 to 15 minutes (and about 2 GB) - depends on which version of Premiere Elements that you are using whether 10 or 15 minutes.
However, in recent times YouTube offers an extended time account (only works at the YouTube web site when you upload your 15 minutes plus video there - that YouTube account does not work in the Premiere Elements YouTube feature.
In the past, are you sure that you did not upload a file saved to the computer hard drive to YouTube at the YouTube web site or upload to Vimeo using the Premiere Elements feature.
If you need help with the details of exporting your Timeline content to a file that can be uploaded to YouTube at the YouTube web site with your extended account, please do not hesitate to let me know.