slicer

The slicer is no longer allowing me to select 'Month' from the date hierarchy. It will only allow me to select year. This function worked before and works if the report already has the slicer set to Month. However, if you drag the same date field to the report, change it to a slicer, and then tell it to use Date Hierarchy, only the Year will show. I've tried various ways to trick it (such as deleting all but the Month from the date hierarchy before changing it to a slicer). Thank you