While you don't mention which operating system you're using, the problem should be solvable.
While in Score Manager, you also need to set the Percussion MIDI Maps to match the Percussion Layout. These are two separate items. The column for the Percussion MIDI Maps is on the far right of the main (upper) portion of the window. If you don't see the column, use the Customize button just below the upper portion and check that the column is to be visible.
While in Score Manager, you also need to set the Percussion MIDI Maps to match the Percussion Layout. These are two separate items. The column for the Percussion MIDI Maps is on the far right of the main (upper) portion of the window. If you don't see the column, use the Customize button just below the upper portion and check that the column is to be visible.