This feature is controlled in the Scheduler Settings and is the default setting. However, if this option was changed during setup and you need to change it back, you can follow these steps:
1. Open any schedule in MSP
2. Go to the Schedule menu at the top of the window and select "Scheduler Settings..."
3. In the Special Services section at the bottom, choose "Schedule any volunteer for any special service (regardless of his or her service preferences)"
4. Click OK