Error configuring Crashlytics in Xcode

I'm trying to add Crashlytics to my project but I have a problem / error since I do not get errors in the Firebase

This is my pofile

source 'https://github.com/CocoaPods/Specs.git'
use_frameworks!
swift_version = "4.0"

target "BProject Name" do

    pod 'Firebase/Core'
    pod 'Firebase/Messaging'
    pod 'Fabric', '~> 1.7.2'
    pod 'Crashlytics', '~> 3.9.3'
end

This is my code for the error:

@IBAction func volver(_ sender: UIBarButtonItem) {
    Crashlytics.sharedInstance().crash()
}

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    //FIREBASE
    FirebaseApp.configure()
    Fabric.sharedSDK().debug = true
    Messaging.messaging().delegate = self
    return true
}

I followed the instructions on the Google Documentation but it does not work for me. I do not get the errors in the Firebase console.

Any possible solution?