Please try this first.
Remove Youtube from Account Preference, then add it back and be sure all permissions are granted during authentication. And please make sure it's an active YouTube channel.
Please make sure that:
There is at least one social profile selected in Publish Editor. You need to click 'Add a video' and upload a video. Then it will show the YouTube channel options. We are making a change soon to allow publishing to YouTube even when no social profiles are selected.