Try the instructions under "Revert to factory settings" in the Handbook. If that doesn't work, please ask for help in the Support forum (or use "Help / Ask for Help" in MuseScore), and include information about your OS and the settings you see in Edit / Preferences / I/O. But do the revert first; it will fix any installation problem that may be causing this.
Comments
Try the instructions under "Revert to factory settings" in the Handbook. If that doesn't work, please ask for help in the Support forum (or use "Help / Ask for Help" in MuseScore), and include information about your OS and the settings you see in Edit / Preferences / I/O. But do the revert first; it will fix any installation problem that may be causing this.