Pitch correction issues

I have a pre-recorded song on GarageBand and Im trying to use this app to add pitch corrected vocals to it. The song is in A# Major. I set the app to A# Major with the pitch correction at 100% and it sounded extremely flat still. I played the scale on piano and the notes were correct but for some reason the autotune still lets the notes come up very flat. If there is something I can do to fix this, please let me know!

EricRayMiller about Auto-Tune Mobile