ProgramChange to Switch Instrument?

Hello (Again) Folks,

If I use the web interface, I can change instruments to those in the Samples directory. I can't, however, change from my midi controller.

I am using an Akai MPK Mini mk3. There is. "Prog Change" toggle button; after pressing that button, the drumpads send "Prog Change" messages. I used the midimon program to check. Here are what the drum pads send when Prog Change is not pressed; and then when it is (in green):

Started /dev/ttyAMA0 as MIDI device "SERIALPORT"
Opened SERIALPORT for MIDI OUT
Listening on SERIALPORT for MIDI IN

..sensing MIDI ports except serial/UART (dealt with above)..
MIDI in:
  - MPK mini 3 24:0
MIDI out:
  - MPK mini 3 24:0
Open "MPK mini 3 24:0" as MIDI IN 1 
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOn 36=C2, velocity=38
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOff 36=C2, velocity=0
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOn 37=C#2, velocity=25
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOff 37=C#2, velocity=0
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOn 38=D2, velocity=23
"MPK mini 3 24:0" (3 bytes) Channel 10, NoteOff 38=D2, velocity=0
"MPK mini 3 24:0" (2 bytes) Channel 10, ProgramChange 0 (=1 for humans)
"MPK mini 3 24:0" (2 bytes) Channel 10, ProgramChange 1 (=2 for humans)
"MPK mini 3 24:0" (2 bytes) Channel 10, ProgramChange 2 (=3 for humans)

So it looks like it the controller is sending the right messages? Is there something I need to do get SamplerBox to recognize that signal?

(I've read about keynotes.csv, but I don't understand its relevant for ProgChange messages; and, to be honest, I've had trouble even getting the pads to register in any capacity.)

Thanks in advance.

Chris