Why isn't my rx subscription triggered on my onNext?

Playing around with Rx Swift I have run into a situation where my subscription doesn't trigger.

I have two viewControllers. The first has a label that the subscriber should update, like this:

func listen() {
   print("In func")
   let sec = storyboard?.instantiateViewController(withIdentifier: "secondvc") as! SecondViewController

   sec.myRx.subscribe(onNext: {
    print("SUBSCRIBED", $0)
       self.rxLabel.text = $0
   })
}

If you go to the sencond viewController there is a button that sets off an onNext event. Like this:

    var myRx = PublishSubject<String>()

    @IBAction func myButton(_ sender: Any) {
        myRx.asObserver().onNext("Hello")
    }

So, in my head, when myButton is pressed in the second viewController the label in the first viewController should update when going back to that viewController. But from what I can tell, the function is triggered, but the subscription isn't triggered at all.

Please make sure you are subscribing to the same PublishSubject you're posting events to. Easiest way to confirm this is to by setting breakpoints and checking the address.