I don't know if it's still the case, but when I first started using Nostr I ran into a situation where Alby decided to make an nsec for me instead of using my real nsec. The settings are in the "wallet" area, (even if you aren't using their wallet) and the text descriptions aren't very clear.
If you play around with that, and still can't figure it out, I'd choose a different extension. Alby has gotten worse in the last year or so, by popping up new tabs every time I sign in. It used to be slick and seamless, now it's kind of a pain.
