Can't retrieve data from firebase realtime database and display in table view

I have been trying to retrieve profile data from firebase realtime database and displaying it in a table view, so far when I run the simulator the tabelview shows up blank and Failed : error 0:50 [50] shows up. I am pretty new to swift and am not sure what the problem is.

Here is my code:

import UIKit
import FirebaseDatabase
import FirebaseStorage
import FirebaseAuth

class userViewController: UIViewController, UITableViewDelegate, UITableViewDataSource{
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
         return profileData.count
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "firstName_cell",
                                                 for: indexPath)

        cell.textLabel?.text = self.profileData[indexPath.item]
        return cell
    var profileData = [String]()
    let storageRef =
    var databaseRef = Database.database().reference()
    var ref: DatabaseReference?
    @IBOutlet var tableView: UITableView!
    override func viewDidLoad() {
        ref = Database.database().reference()
        //let userID = Auth.auth().currentUser?.uid
        ref?.child("users").observeSingleEvent( of: .childAdded, with: { (snapshot) in
            let profile = snapshot.value as? String
            if let actualProfile = profile{
              }) { (error) in


Add a breakpoint here

are you getting any data at all?

What is the error actually saying?

Do you have the proper permissions to read?

At the breakpoint it prints: 2020-08-11 09:34:34.048712+0400 [Storyboard] Unknown class profileTableView in Interface Builder file.

and the database rules are set as:

“rules”: {
“.read”: “auth !=null”,
“.write”: “auth !=null”

I have just changed the rules to true, but the tableview still isn’t displaying data