It is an epidemic! Several reports from different countries. And, I am confirming (in USA East) the HTTP 500 error with at least Premiere Element 12/12.1 and 13/13.1 on Windows 7 64 bit and Windows 10 64 bit.
As I mentioned in the other threads on the matter that have been appearing today, this appears to be a YouTube server problem that needs fixing by YouTube...a sort of wait and see on the part of the user.
Until the fix, please try to export your Timeline content to an AVCHD.mp4 file, and then upload that AVCHD.mp4 file to YouTube at the YouTube web site.
Any questions or need clarification, please do not hesitate to ask.