Hmm that's strange. Perhaps you have two Google accounts with different subscriptions? When you sign in I grab your subscribed channels and that's what I send when you categorise. You can check the "Subscriptions" page to see exactly what data we pulled.

I did say Chrome browser because with the deprecation of manifest v2, I had to make a choice about which to support. I decided given Chrome's larger market share that it would benefit the most people sooner. However I'm building it in such a way that porting to Firefox shouldn't require much additional work.

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