shifting notes rightwards using SHIFT right arrow

I have probably missed something here but I'm trying to shift 3 adjacent notes in a measure to the right using SHIFT + the right arrow key. This works fine in that a rest of the correct duration is inserted to fill the space vacated, but the piece still plays as if the notes are in the same place! I tried making the shift larger with more SHIFT+arrow key, and while the notation is always correctly adjusted, the piece still plays, as I say, as if the notes hadn't been moved.
regards
-John