My understanding is that tags should be available across all notebooks.
However when I create a new notebook, and then a new note, when I click on the add tag icon, I don’t see a list of all my available tags. However, if I start typing a tag name, it does generate a drop-down list with all the existing tags that start with that letter.
In my original notebook, clicking that link immediately shows me a list with all tags which is what I want, so I’m not having to type out all possible starting letters.
I’m using Evernote on my iPad (not web version) and have personal account. I’m using iOS 17.1.1