firebase, swift, ios - Failed to fetch default token Error Domain=com.firebase.iid Code=6 "(null)"

Question

I'm making a login app that tracks whether someone is logged in or not. I'm using firebase as a way to do this. if a person is not in firebase, they cannot be logged in.

PROBLEM

I keep getting the console error

<FIRInstanceID/WARNING> Failed to fetch default token Error Domain=com.firebase.iid Code=6 "(null)"

when I simulate the app. when I try to log in as Ash Dreyer, it does not log me in. I click it several times so even though I am logged in in firebase, it should log me out and log me back in again.

FIREBASE

{
  "Ash Dreyer" : {
    "activity" : "None",
    "current_status" : "IN",
    "num_of_logins" : 0,
    "total_hours" : 0,
    "type" : "mentor"
  },
  "Bryton Moeller" : {
    "activity" : "None",
    "current_status" : "OUT",
    "num_of_logins" : 0,
    "total_hours" : 0,
    "type" : "student"
  }
}

APP DELEGATE

import UIKit
import Firebase

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    override init() {
        FIRApp.configure()
    }

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        FIRApp.configure()
        return true
    }
}

LOGINVIEWCONTROLLER

import Firebase
import UIKit

class LoginViewController: UIViewController {
    @IBOutlet weak var activity_label: UILabel!
    @IBOutlet weak var activity_picker: UIPickerView!
    @IBOutlet weak var name_field: UITextField!
    @IBOutlet weak var login_button: UIButton!
    @IBOutlet weak var location_switch: UISwitch!

    var root_ref = FIRDatabase.database().reference()

    // Color scheme
    let grey = UIColor(red: 0.933, green: 0.929, blue: 0.922, alpha: 1.0)
    let dark_orange = UIColor(red: 0.769, green: 0.396, blue:  0.176, alpha: 1.0)
    let dark_blue = UIColor(red: 0.188, green: 0.463, blue: 0.541, alpha: 1.0)
    let light_blue = UIColor(red: 0.412, green: 0.663, blue: 0.686, alpha: 1.0)
    let light_orange = UIColor(red: 0.871, green: 0.612, blue: 0.451, alpha: 1.0)

    var user: Person!

    func update_UI() {
        if let _ = user {
            if user!.current_status == "IN" {
                login_button.setTitleColor(dark_blue, for: UIControlState.normal)
                login_button.setTitle("LOG OUT", for: UIControlState.normal)
            } else {
                login_button.setTitleColor(dark_orange, for: UIControlState.normal)
                login_button.setTitle("LOG IN", for: UIControlState.normal)
            }
        }
    }

    func login(member: inout Person) {
        if member.current_status == "IN" {
            member.current_status = "OUT"
        } else {
            member.current_status = "IN"
        }

        root_ref.child(byAppendingPath: member.key).updateChildValues(["current_status": member.current_status]);

        update_UI()
    }

    func login_new_user(member_name: String) {
        root_ref.observe(FIRDataEventType.value, with: { (snapshot) -> Void in
            for member in snapshot.children {
                if member.key == member_name {
                    self.user = Person(snapshot: member as! FIRDataSnapshot)
                }
            }
        })

        if let _ = user {
            login(member: &user!)
        }
    }

    @IBAction func login_user(_ sender: UIButton) {
        if let _ = user, let name_text = name_field.text, name_text != "" {
            if user.key != name_text {
                login_new_user(member_name: name_text)
            }
        } else if let name_text = name_field.text, name_text != "" {
            login_new_user(member_name: name_text)
        } else if let _ = user {
            login(member: &user!)
        } else {
            print("Please enter text into the text field")
        }
    }

    @IBAction func toggle_location(_ sender: UISwitch) {

    }

    @IBAction func other_login(_ sender: UIButton) {

    }
}

NOTES

• when I just had FIRApp.configure() in func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool, it gave me a SIGABRT error.
• it's a small group that we are tracking, so I've decided to use first names instead of UIDs.
• I'm using firebase 3

Answer 1

Just to update, these errors should no longer appear in the latest version of Firebase when using the Xcode 8.2+ version of the simulator. There was an issue (in fact a couple) with the simulator, and some overly aggressive logging in InstanceID.