In order to assist, we would need you to attach the score you are having trouble with and give us precise steps to reproduce the problem. Also tell us what OS, what version of MuseScore as per Help / About, what settings you see in Edit / Preferences / I/O, what soundfonts you have loaded in View / Synthesizer, and where the volume is set in that same dialog.
Comments
In order to assist, we would need you to attach the score you are having trouble with and give us precise steps to reproduce the problem. Also tell us what OS, what version of MuseScore as per Help / About, what settings you see in Edit / Preferences / I/O, what soundfonts you have loaded in View / Synthesizer, and where the volume is set in that same dialog.