Same here. Noticed it this afternoon. The fixes listed so far in this thread (when signed in) didn’t help. Chatted with a tech agent. She said something to the effect that “we haven’t heard anything about this problem since noon (noon in Delhi?). I told her that just because she hadn’t heard about it lately doesn’t mean it’s fixed. So, Roku knows about the problem. I just can’t figure out why Roku can’t put a trouble advisory on their website or app so we can see that they know about and are working on a problem.
You chatted with the wrong support agent (Roku support of course cant tell you about YT's issue etc) - you need to contact Google/YT - its their app and their authentication issue .