hi im trying to make real time sound effect app I managed to add pitch and reverb adjuster and now I want to control left and right channels tried AVAudioPlayerNode.pan and did not effect the output and tried mainmixernode and didnt work

import UIKit
import AVFoundation

class ViewController: UIViewController {

    var audioEngine: AVAudioEngine!
    var pitchEffect: AVAudioUnitTimePitch!
    var reverbEffect: AVAudioUnitReverb!
    var delayEffect: AVAudioUnitDelay!
    var audioSession: AVAudioSession!
    var playerNode: AVAudioPlayerNode!
    var mixerNode: AVAudioMixerNode!
    
    // Additional property for balance
    var balanceSlider: UISlider!

    override func viewDidLoad() {
        super.viewDidLoad()
        requestMicrophonePermission()
    }

    func requestMicrophonePermission() {
        audioSession = AVAudioSession.sharedInstance()
        do {
            try audioSession.setCategory(.playAndRecord, mode: .default, options: [.defaultToSpeaker, .allowBluetoothA2DP, .allowBluetooth])
            try audioSession.setActive(true, options: .notifyOthersOnDeactivation)
            
            audioSession.requestRecordPermission { granted in
                DispatchQueue.main.async {
                    if granted {
                        print("Microphone access granted")
                        self.setupAudioEngine()
                        self.startAudioEngine()
                        self.setupUI()
                    } else {
                        print("Microphone access denied")
                    }
                }
            }
        } catch {
            print("Failed to set up audio session: (error.localizedDescription)")
        }
    }

    func setupAudioEngine() {
        audioEngine = AVAudioEngine()
        playerNode = AVAudioPlayerNode()
        pitchEffect = AVAudioUnitTimePitch()
        pitchEffect.pitch = 0 // Default pitch value
        reverbEffect = AVAudioUnitReverb()
        reverbEffect.loadFactoryPreset(.mediumRoom)
        reverbEffect.wetDryMix = 0 // Default reverb value
        delayEffect = AVAudioUnitDelay()
        delayEffect.delayTime = 0 // Default delay time in seconds
        
        // Create mono format
        let monoFormat = AVAudioFormat(standardFormatWithSampleRate: 44100, channels: 1)

        mixerNode = audioEngine.mainMixerNode
        mixerNode.outputVolume = 0.5 // Default volume

        let inputNode = audioEngine.inputNode
        let inputFormat = inputNode.inputFormat(forBus: 0)

        audioEngine.attach(playerNode)
        audioEngine.attach(pitchEffect)
        audioEngine.attach(reverbEffect)
        audioEngine.attach(delayEffect)
        
        // Connect nodes with mono format
        audioEngine.connect(playerNode, to: pitchEffect, format: inputFormat)
        audioEngine.connect(pitchEffect, to: reverbEffect, format: inputFormat)
        audioEngine.connect(reverbEffect, to: delayEffect, format: inputFormat)
        audioEngine.connect(delayEffect, to: mixerNode, format: inputFormat)
        audioEngine.connect(mixerNode, to: audioEngine.outputNode, format: monoFormat)
        mixerNode.pan = 1
        
        inputNode.installTap(onBus: 0, bufferSize: 1024, format: inputFormat) { [weak self] (buffer, when) in
            guard let self = self else { return }
            
            self.processMonoAudioBuffer(buffer)
            self.playerNode.scheduleBuffer(buffer, completionHandler: nil)
        }
    }

    func processMonoAudioBuffer(_ buffer: AVAudioPCMBuffer) {
        let channels = buffer.format.channelCount
        if channels > 1 {
            let leftChannel = buffer.floatChannelData?[0]
            let rightChannel = buffer.floatChannelData?[1]
            
            if let left = leftChannel, let right = rightChannel {
                for i in 0..<Int(buffer.frameLength) {
                    let average = (left[i] + right[i]) / 2
                    left[i] = average
                    right[i] = average
                }
            }
        }
    }

    func startAudioEngine() {
        do {
            try audioEngine.start()
            playerNode.play()
            print("Audio engine started")
        } catch {
            print("Failed to start audio engine: (error.localizedDescription)")
        }
        mixerNode.pan = 1
    }

    func setupUI() {
        let pitchSlider = UISlider(frame: CGRect(x: 96, y: 460, width: 200, height: 10))
        pitchSlider.minimumValue = -1000 // -2 octaves
        pitchSlider.maximumValue = 1000 // +2 octaves
        pitchSlider.value = 0 // Default pitch shift
        pitchSlider.addTarget(self, action: #selector(pitchSliderChanged(_:)), for: .valueChanged)
        view.addSubview(pitchSlider)

        let reverbSlider = UISlider(frame: CGRect(x: 96, y: 512, width: 200, height: 10))
        reverbSlider.minimumValue = 0 // 0% reverb
        reverbSlider.maximumValue = 100 // 100% reverb
        reverbSlider.value = 0 // Default reverb
        reverbSlider.addTarget(self, action: #selector(reverbSliderChanged(_:)), for: .valueChanged)
        view.addSubview(reverbSlider)

        let delaySlider = UISlider(frame: CGRect(x: 96, y: 572, width: 200, height: 10))
        delaySlider.minimumValue = 0 // 0 seconds
        delaySlider.maximumValue = 2 // 2 seconds
        delaySlider.value = 0 // Default delay time
        delaySlider.addTarget(self, action: #selector(delaySliderChanged(_:)), for: .valueChanged)
        view.addSubview(delaySlider)
        
        let volumeSlider = UISlider(frame: CGRect(x: 96, y: 625, width: 200, height: 10))
        volumeSlider.minimumValue = 0 // Mute
        volumeSlider.maximumValue = 1 // Full volume
        volumeSlider.value = 0.5 // Default volume
        volumeSlider.addTarget(self, action: #selector(volumeSliderChanged(_:)), for: .valueChanged)
        view.addSubview(volumeSlider)
        
        // Add balance slider
        balanceSlider = UISlider(frame: CGRect(x: 96, y: 675, width: 200, height: 10))
        balanceSlider.minimumValue = -1 // Fully left
        balanceSlider.maximumValue = 1 // Fully right
        balanceSlider.value = 0 // Center
        balanceSlider.addTarget(self, action: #selector(balanceSliderChanged(_:)), for: .valueChanged)
        view.addSubview(balanceSlider)
    }

    @objc func pitchSliderChanged(_ sender: UISlider) {
        pitchEffect.pitch = sender.value
    }

    @objc func reverbSliderChanged(_ sender: UISlider) {
        reverbEffect.wetDryMix = sender.value
    }

    @objc func delaySliderChanged(_ sender: UISlider) {
        delayEffect.delayTime = TimeInterval(sender.value)
    }
    
    @objc func volumeSliderChanged(_ sender: UISlider) {
        mixerNode.outputVolume = sender.value
    }
    
    @objc func balanceSliderChanged(_ sender: UISlider) {
        let panValue = sender.value
        mixerNode.pan = panValue
    }
}

tried AVAudioPlayerNode.pan and did not effect the output and tried mainmixernode and didnt wo