Have you verified that you have a channel created within your Youtube account?

If you look at the top right corner of the Youtube page; Do you see your e-mail address or do you see a username?

If you see an e-mail address, that would mean you still need to create a channel for your youtube account.

Also, are you positive that you have linked your Youtube account to your ELITE account properly? You can follow these directions to be sure:

http://goo.gl/HtZwX (To unlink)

http://goo.gl/UWP2v (To link)

Finally, make sure that Call of Duty ELITE has permission within your Youtube account (This can be found under your Youtube account settings).