I use AVMIDIPlayer to play music, some devices do not have sound, click System Settings > general purpose > restore to solve. What is the reason for this?

I use AVMIDIPlayer to play music, some devices do not have sound, click System Settings > general purpose > restore to solve. What is the reason for this?

import UIKit

import AVKit

class ViewController: UIViewController {

var avplayer : AVMIDIPlayer?

override func viewDidLoad() {

super.viewDidLoad()

let filePatch = Bundle.main.path(forResource: "xiaobuwuqu", ofType: "mid")

let sfTowPatch = Bundle.main.path(forResource: "TimGM6mb", ofType: "sf2")

let data = try? Data(contentsOf: URL(fileURLWithPath: filePatch!))

avplayer = try? AVMIDIPlayer(data: data!, soundBankURL: URL(fileURLWithPath: sfTowPatch!))

avplayer?.prepareToPlay()

}

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {

avplayer?.currentPosition = 0

avplayer?.play({

})

print(avplayer?.isPlaying)

}

}