Garageband's nunits cc 123 all notes off does not work

I have this software in a MacOS app that provides an All Notes Off button. When I start notes playing with the sendNoteOn function, I cannot get GarageBand to quiet/stop playing the notes.

func notesOffFor(channel: UInt8 ) {

guard connected, let dest = destination else { return }

var packetList = MIDIPacketList()

var packet = MIDIPacketListInit(&packetList)

let midiStatus : UInt8 = 0xB0 | (channel & 0xF)

let allNotesOff = [midiStatus, 123, 0]

packet = MIDIPacketListAdd(&packetList, 1024, packet, 0, allNotesOff.count, allNotesOff)

print("created packet: \(packet.pointee.length)=>\(packet.pointee.data)")

let res = MIDISend(outputPort, dest, &packetList)

print("sending all notes off for channel=\(channel) returns=\(res)")

}

func notesOffFor(channel: UInt8 ) {

guard connected, let dest = destination else { return }

var packetList = MIDIPacketList()

var packet = MIDIPacketListInit(&packetList)

let midiStatus : UInt8 = 0xB0 | (channel & 0xF)

let allNotesOff = [midiStatus, 123, 0]

packet = MIDIPacketListAdd(&packetList, 1024, packet, 0, allNotesOff.count, allNotesOff)

print("created packet: \(packet.pointee.length)=>\(packet.pointee.data)")

let res = MIDISend(outputPort, dest, &packetList)

print("sending all notes off for channel=\(channel) returns=\(res)")

}

These functions show a zero return code, and the notes I am testing with all play on separate tracks, and I have a loop that calls notesOffFor(), for all channels 0-15. Is it not possible to use this CC for the built in Midi controller in GarageBand?