I am having exactly the same problem, I've been trying for two days to get my video to publish onto YouTube. It renders all ok but as soon as I hit publish, I get this error.
I'm having the same problem, but keep in mind you can upload your locally rendered file to Youtube via the normal Youtube Studio workflow.
That being said, the Youtube feature should either work consistently or be removed by Adobe - I haven't been able to publish to Youtube via Rush for the last few versions (Mac OS Big Sur v11.2.3).
did you ever figure that proble ? I have the same thing happening to me for the past two days ..
No. It still doesn't work. 🥲