Scoring for bass or bass guitar

When you add a bass from the instruments dialog this is the default behavior. How are you adding a bass to your scores? Can you attach an example of the problem?

If you created the score for bass to begin with, this happens automatically. if you created it for another instrument and then changed the playback sound only, then the thing to do is change the actual instrument, by right clicking the staff, Staff Properties, Change Instrument. If you entered the notes at the correct sounding pitch, all will work automatically. If you entered them at the correct written pitch, you'll now need to transpose them down (select all, Ctrl+Down), but any future notes you enter will be correct automatically.

If that doesn't help, please attach your score and we can advise better.