Signups aren’t per box, it rather works seed run by seed run.
You sign up in each co-op seed run thread you’re interested in. Usually there’s a post like this one where you can add your name in.
And then twice a year a box is sent with the beans of the seeds runs where you put your name in. If you didn’t sign in any seed run, no box.
G-Pas links explain it all. Don’t hesitate to ask if help is needed, public or PM.
Hope everything is alright @G-paS !