This is a user to user forum. Nobody on this forum works for Adobe or YouTube (and YouTube is more likely where the problem lies, since Premiere Elements hasn't changed).
So your guess is as good as ours, and only YouTube knows for sure.
Have you tried outputting an AVCHD (the the YouTube preset) and manually uploading it to YouTube in the meantime?
Daniel Chapman 34
It is now 8:30 pm Sunday March 23, 2014 where I am and as of this moment uploads to YouTube from within Premiere Elements continue to fail with the Online Services message. This is true for at least Premiere Elements 9.0/9.0.1, 10, 11, and 12. The reason for this failure is unknown at the user to user level. While YouTube is failing in this regard, Vimeo is OK at my computer.
My replies are encouraging users to export their Timelines to a file saved to the computer hard drive and from there upload the file to YouTube at the YouTube web site. In the case of Premiere Elements 12, I would suggest that you look at Publish+Share/Computer/AVCHD and one of its AVCHD.mp4 choices for the file to be used in the workaround. I see where SG is suggesting the same approach.
I am sure Adobe and YouTube have the explanation for this but have not shared that explanation with any of us yet.
Looks to be working now as at 24th March 2014 14:20 GMT.
Insanity is hereditary, you get it from your children
If this post or another user's post resolves the original issue, please mark the posts as correct and/or helpful accordingly. This helps other users with similar trouble get answers to their questions quicker. Thanks.
Daniel Chapman 34
As of early this morning, the uploads to YouTube from within Premiere Elements 9.0/9.0.1, 10, 11, and 12 have been working for me. Others have reported this upload working for them in their particular Premiere Elements programs.
If you should continue to have problems with your Premiere Elements 12 Publish+Share/Social Websites/YouTube, please do not hesitate to post and let us know the details so that we can try to sort them out.
Hope only good news about YouTube uploads moving forward.