Swift Admob奖励Ad仅加载一次（对于新实现-迁移代码），并生成错误（“已使用.Ad对象”）

我遗留的Admob rewardedAd实现运行良好。今天我更新了新的实现，但它无法正常工作。除了Admob Swift代码有问题外（返回对象而不返回函数声明中的任何内容）…总之：

我能够创建并加载初始的RewardedAd

当按下触发rewardedAd的按钮（通过通知）时，它会从调试器生成以下消息（“已呈现奖励广告”，紧接着是“未呈现奖励广告”和错误消息“加载失败：错误域=com.google.admob Code=18”演示错误：由于使用了ad对象，将不显示ad。“UserInfo={NSLocalizedDescription=演示错误：由于使用了ad对象，将不显示ad。”

关于上面的步骤2，生命周期从未经历过“rewardedAd”或“RewardedadDidDisclose”并触发“奖励广告未能呈现”而从未尝试呈现新广告

不确定源错误可能是什么，如果您能帮助解决此问题，我们将不胜感激。谢谢

我的实现如下（严格遵循google代码）：

var rewardedAd: GADRewardedAd?

override func viewDidLoad() {
  ...
  createAndLoadRewardedAd()
  ...
{

/// creating the rewarded ad
func createAndLoadRewardedAd() {

        rewardedAd = GADRewardedAd(adUnitID: "ca-app-pub-3940256099942544/1712485313")
        rewardedAd?.load(GADRequest()) { error in
          if let error = error {
            print("Loading failed: \(error)")
          } else {
            print("Loading Succeeded")
          }
        }
    }

/// Lifecycle

/// Tells the delegate that the user earned a reward.
    func rewardedAd(_ rewardedAd: GADRewardedAd, userDidEarn reward: GADAdReward) {

        print("Reward received with currency: \(reward.type), amount \(reward.amount).")
    }
    /// Tells the delegate that the rewarded ad was presented.
    func rewardedAdDidPresent(_ rewardedAd: GADRewardedAd) {
      print("Rewarded ad presented.")
    }
    /// Tells the delegate that the rewarded ad was dismissed.
    /// Load another ad upon dismissing the previous
    func rewardedAdDidDismiss(_ rewardedAd: GADRewardedAd) {
      print("RewardAd did dismiss")
      createAndLoadRewardedAd()

    }
    /// Tells the delegate that the rewarded ad failed to present.
    func rewardedAd(_ rewardedAd: GADRewardedAd, didFailToPresentWithError error: Error) {
        print("Rewarded ad failed to present.")
        print("Loading failed: \(error)")

    }

    /// Used by Notification Observer to present rewardedAd
    @objc func startRewardVideoAd() {
        if rewardedAd?.isReady == true {
           rewardedAd?.present(fromRootViewController: self, delegate:self)
        } else {
            print("Reward based video not ready")
        }
    }