Are you are running the package in the debian repository? IIRC, they modified the scripts, so perhaps it doesn't source soundon.user on startup. I suggest uninstalling it and using the deb from this website - it's a newer build too (debian still has b2003).
If what I said above is wrong, try to run "sudo soundoff" and "sudo soundon" script to test the startup. Ideally, the soundon script should run the soundon.user file. If not, try inserting echo commands for debugging (e.g. in soundon.user) and see where it stops.