rewardedAdDidDismiss function not getting called - swift

Question

I'm implementing rewarded ads in a chat application and using tab bars with it. I'm having a problem with rewarded that whenever I call the function rewardedAd = createAndLoadRewardedAd() in viewDidLoad and the ad gets presented when I dismiss the ad the function rewardedAdDidDismiss gets called without a problem.
override func viewDidLoad() {
super.viewDidLoad()
timerLabelDisplay.layer.opacity = 0.0
rewardedAd = createAndLoadRewardedAd()
}
Now as we all now viewDidLoad will be called only one time, and this will not help me if i change the tab bar and get back to it, this mean my ad won't load. So what i did, is i put the rewardedAd = createAndLoadRewardedAd() in viewWillAppear
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
removeAdsFreeButton.isEnabled = false
removeAdsFreeButton.backgroundColor = .gray
rewardedAd = createAndLoadRewardedAd()
}
Now when i did this everything seems to be perfect, when i change the tab bar and go back again, my reward ad is loading without a problem. However now, when the ad is dissmissed, the function rewardedAdDidDismiss() is not getting called, and i need it to be called and i didn't know why?
here it is the full code:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
removeAdsFreeButton.isEnabled = false
removeAdsFreeButton.backgroundColor = .gray
rewardedAd = createAndLoadRewardedAd()
}
override func viewDidLoad() {
super.viewDidLoad()
timerLabelDisplay.layer.opacity = 0.0
}
func createAndLoadRewardedAd() -> GADRewardedAd? {
rewardedAd = GADRewardedAd(adUnitID: "ca-app-pub-3940256099942544/1712485313")
rewardedAd?.load(GADRequest()) { error in
if error != nil {
print("Loading reward ad failed there is a problem here")
} else {
UIView.animate(withDuration: 1.0) {
self.removeAdsFreeButton.isEnabled = true
self.removeAdsFreeButton.layer.backgroundColor = UIColor(named: "ChatiwRed")!.cgColor
self.removeAdsFreeButton.layer.backgroundColor = UIColor(named: "ChatiwYello")!.cgColor
self.removeAdsFreeButton.layer.backgroundColor = UIColor(named: "ChatiwRed")!.cgColor
}
self.removeAdsFreeButton.pulseAnimation()
}
}
return rewardedAd
}
var didUserGotReward = false
func rewardedAdDidDismiss(_ rewardedAd: GADRewardedAd) {
self.rewardedAd = createAndLoadRewardedAd()
print("ok now show the timer")
if didUserGotReward {
UIView.animate(withDuration: 5) {
self.timerLabelDisplay.layer.opacity = 1.0
}
timerLabelDisplay.pulseAnimation()
didUserGotReward = false
}
}