Не читаются данные из Firebase Realtime Database

package com.example.heartbeatapp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.ArrayAdapter
import android.widget.ListView
import com.google.firebase.auth.ktx.auth
import com.google.firebase.database.DataSnapshot
import com.google.firebase.database.DatabaseError
import com.google.firebase.database.DatabaseReference
import com.google.firebase.database.FirebaseDatabase
import com.google.firebase.database.ValueEventListener
import com.google.firebase.ktx.Firebase

class RedactProfilePage : AppCompatActivity() {
    private lateinit var list: ListView
    private lateinit var adapter :ArrayAdapter<String>
    private lateinit var listData: List<String>
    private val auth = Firebase.auth
    private val currentUser = auth.currentUser
    private val USER_KEY = "Users"
    private var databaseReference =
        currentUser?.let { FirebaseDatabase.getInstance().getReference(USER_KEY).child(it.uid) }


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.redact_profile_page)
        init()
        getNameDataFromDb()
    }

    private fun init(){
        list = findViewById<ListView>(R.id.list)
        listData = ArrayList()
        adapter = ArrayAdapter(this,android.R.layout.simple_list_item_1, listData)
        list.adapter
        databaseReference = currentUser?.let { FirebaseDatabase.getInstance().getReference(USER_KEY).child(it.uid) }
    }

    private fun getNameDataFromDb() {
        val listener = object : ValueEventListener {
            override fun onDataChange(snapshot: DataSnapshot) {
                if (listData.size > 0){
                    (listData as ArrayList<String>).clear()
                }
                for (sn: DataSnapshot in snapshot.children) run {
                    var name: User? = sn.getValue(User::class.java)
                    name?.let { (listData as ArrayList<String>).add(it.name) }
                }
                adapter.notifyDataSetChanged()
            }

            override fun onCancelled(error: DatabaseError) {

            }


        }
        databaseReference?.addValueEventListener(listener)
    }
}