xcodeでGIDSignInButtonがConnectできない

xcodeでGIDSignInButtonがConnectできません。

https://developers.google.com/identity/sign-in/ios/sign-in?ver=swift

のサイトの通り実施していますが、以下の状況です。

ViewControllerのコード

import UIKit

class ViewController: UIViewController, GIDSignInUIDelegate {

    @IBOutlet weak var signInButton: GIDSignInButton!
    @IBOutlet weak var signInButton2: UIButton!

    override func viewDidLoad() {
        super.viewDidLoad()
        GIDSignIn.sharedInstance().uiDelegate = self
    }

    func sign(inWillDispatch signIn: GIDSignIn!, error: Error!) {
        //myActivityIndicator.stopAnimating()
    }

    func sign(_ signIn: GIDSignIn!,
              present viewController: UIViewController!) {
        self.present(viewController, animated: true, completion: nil)
    }

    func sign(_ signIn: GIDSignIn!,
              dismiss viewController: UIViewController!) {
        self.dismiss(animated: true, completion: nil)
    }

    @IBAction func didTapSignOut(sender: AnyObject) {
        GIDSignIn.sharedInstance().signOut()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

StoryBoardでsignInButton2のUIButtonは通常通りコネクトできます。

signInButtonのGIDSignInButtonはコネクトできません。

何か考えられる原因をアドバイスください。
ここまでのコンパイルはできています。

AppDelegateは以下の通りです。

import UIKit
import Google

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, GIDSignInDelegate {
    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        return true
    }

    func applicationWillResignActive(_ application: UIApplication) {
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
    }

    func applicationWillEnterForeground(_ application: UIApplication) {
    }

    func applicationDidBecomeActive(_ application: UIApplication) {
    }

    func applicationWillTerminate(_ application: UIApplication) {
    }

    private func application(application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        // Initialize sign-in
        var configureError: NSError?
        GGLContext.sharedInstance().configureWithError(&configureError)
        assert(configureError == nil, "Error configuring Google services: \(String(describing: configureError))")
        GIDSignIn.sharedInstance().delegate = self
        return true
    }

    @available(iOS 9.0, *)
    func application(_ application: UIApplication, open url: URL, options: [UIApplicationOpenURLOptionsKey : Any])
        -> Bool {
            return GIDSignIn.sharedInstance().handle(url,
                                                        sourceApplication:options[UIApplicationOpenURLOptionsKey.sourceApplication] as? String,
                                                        annotation: [:])
    }

    //for iOS 8, check availability
    @available(iOS, introduced: 8.0, deprecated: 9.0)
    func application(application: UIApplication,openURL url: NSURL, sourceApplication: String?, annotation: AnyObject) -> Bool {
        return GIDSignIn.sharedInstance().handle(url as URL!, sourceApplication: sourceApplication!, annotation: annotation)
    }

    func sign(_ signIn: GIDSignIn!, didSignInFor user: GIDGoogleUser!, withError error: Error!) {
        if (error == nil) {
            // Perform any operations on signed in user here.
            let userId = user.userID                  // For client-side use only!
            let idToken = user.authentication.idToken // Safe to send to the server
            let fullName = user.profile.name
            let givenName = user.profile.givenName
            let familyName = user.profile.familyName
            let email = user.profile.email
            // ...
        } else {
            print("\(error.localizedDescription)")
        }
    }

    func signIn(signIn: GIDSignIn!, didDisconnectWithUser user:GIDGoogleUser!,
                withError error: NSError!) {
        // Perform any operations when the user disconnects from app here.
        // ...
    }
}

よろしくお願いします。