画面遷移が何故かできません

実現したいこと

クリックハンドラーで画面遷移をさせたい
・ボタンタップ→画面遷移
・MainActivity→AddActivityに遷移

発生している問題・エラーメッセージ

特にエラーコードは発生しておらず、ボタンをタップしても何も起こりません。
必要な記述は試しましたが、何が原因で動かないのか分からないので、教えて頂きたいです。

試したこと

・MainActivityにsetOnClickListenerを実装、Intentで画面遷移
・AndroidManifestにactivityの追加

該当のソースコード

▼MainActivity

Kotlin
package com.example.showtextonmapapp

import省略

class MainActivity : AppCompatActivity(), OnMapReadyCallback {

    private lateinit var mMap: GoogleMap
    private val MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION = 1
    private lateinit var fusedLocationProviderClient : FusedLocationProviderClient
    private lateinit var lastLocation: Location
    private var locationCallback : LocationCallback? = null
    private lateinit var realm: Realm

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //画面をスリープにしない
        window.addFlags(FLAG_KEEP_SCREEN_ON)

        // Obtain the SupportMapFragment and get notified when the map is ready to be used.
        val mapFragment = supportFragmentManager
            .findFragmentById(R.id.map) as SupportMapFragment
        mapFragment.getMapAsync(this)
        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this)

        realm = Realm.getDefaultInstance()
        val toAddBtn: Button = findViewById(R.id.toAddBtn)
        toAddBtn.setOnClickListener {
            val intent = Intent(this, AddActivity::class.java)
            intent.putExtra("lat", lastLocation.latitude)
            intent.putExtra("lng", lastLocation.longitude)
            startActivity(intent)
        }
    }

    override fun onMapReady(googleMap: GoogleMap) {
        mMap = googleMap

        checkPermission()
    }

    private fun checkPermission() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            myLocationEnable()
        } else {
            requestLocationPermission()
        }
    }

    private fun requestLocationPermission() {
        if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION)) {
            //許可が拒否された場合
            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION)
        } else {
            //許可も求めていない場合
            ActivityCompat.requestPermissions(this, arrayOf(Manifest.permission.ACCESS_FINE_LOCATION), MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION)
        }
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        when(requestCode) {
            MY_PERMISSION_REQUEST_ACCESS_FINE_LOCATION->{
                if (permissions.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    //許可された
                    myLocationEnable()
                } else {
                    showToast("現在位置は表示できません")
                }
            }
        }
    }

    private fun myLocationEnable() {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED) {
            mMap.isMyLocationEnabled = true
            val locationRequest = LocationRequest().apply {
                interval = 10000
                fastestInterval = 5000
                priority = LocationRequest.PRIORITY_HIGH_ACCURACY
            }
            locationCallback = object : LocationCallback() {
                override fun onLocationResult(locationResult: LocationResult?) {
                    val textView : TextView = findViewById(R.id.textView)
                    if (locationResult?.lastLocation != null) {
                        lastLocation = locationResult.lastLocation
                        val currentLatLng = LatLng(lastLocation.latitude, lastLocation.longitude)
                        mMap.moveCamera(CameraUpdateFactory.newLatLng(currentLatLng))
                        textView.text = "Lat:${lastLocation.latitude}, Lng:${lastLocation.longitude}"
                    }
                }
            }
            fusedLocationProviderClient.requestLocationUpdates(locationRequest, locationCallback, null)
        }
    }

    private fun showToast(msg: String) {
        val toast = Toast.makeText(this, msg, Toast.LENGTH_LONG)
        toast.show()
    }

    override fun onPause() {
        super.onPause()
        if (locationCallback != null) {
            fusedLocationProviderClient.removeLocationUpdates(locationCallback)
        }
    }

    override fun onDestroy() {
        super.onDestroy()
        realm.close()
    }

}

▼AddActivity.kt

Kotlin
package com.example.showtextonmapapp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import android.widget.Toast
import io.realm.Realm
import io.realm.kotlin.createObject
import io.realm.kotlin.where
import java.util.*

class AddActivity : AppCompatActivity() {
    private lateinit var realm: Realm

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_add)
        realm = Realm.getDefaultInstance()

        val lat = intent.getDoubleExtra("lat", 0.0)
        val lng = intent.getDoubleExtra("lng", 0.0)
        val saveBtn: Button = findViewById(R.id.saveBtn)
        val cancelBtn: Button = findViewById(R.id.cancelBtn)

        saveBtn.setOnClickListener {
            val editText: EditText = findViewById(R.id.editText)
            val shopInfoStr = editText.text?.toString() ?: ""
            realm.executeTransaction {
                val maxId = realm.where<ShopInfo>().max("id")
                val nextId = (maxId?.toLong() ?: 0L) + 1L
                val shopInfo = realm.createObject<ShopInfo>(nextId)
                shopInfo.dateTime = Date()
                shopInfo.lat = lat
                shopInfo.lng = lng
                shopInfo.shopInfo = shopInfoStr
        }
            showToast("保存しました")
            finish()
        }
        cancelBtn.setOnClickListener {}
        finish()
    }

    override fun onDestroy() {
        super.onDestroy()
        realm.close()
    }

    private fun showToast(msg: String) {
        val toast = Toast.makeText(this, msg, Toast.LENGTH_LONG)
        toast.show()
    }
}

▼activity_add.xml

Kotlin
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".AddActivity">

    <EditText
        android:id="@+id/editText"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="150dp"
        android:layout_marginEnd="100dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text=""
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.497"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/saveBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="100dp"
        android:layout_marginTop="250dp"
        android:text="保存"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/cancelBtn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="250dp"
        android:layout_marginEnd="100dp"
        android:text="キャンセル"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="100dp"
        android:text="テキストを入力してください"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

▼AndroidManifest.xml

Kotlin
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.showtextonmapapp">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

    <application
        android:name=".CustomApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ShowTextOnMapApp">
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".AddActivity" />
    </application>

</manifest>