I do have multiple YouTube accounts (channels) under one Google account. I initially logged in as one YouTube channel of mine that I wanted to categorize. Only then did I find out that it looks at subscriptions. So I logged out and logged back in as my main account which is subscribed to the other one. Then I hit the problem.
Hmm okay. Maybe some wires got crossed in the back end. Perhaps Google OAuth doesn't distinguish between accounts and associated both sets of subscriptions with the same user? Interesting
