rewarded ads value null flutter

Question

In my test application, when ontap is running, I want to show the award-winning ad with seconds and then the quiz to be loaded and the questions to be loaded. How can I do this? The code below does not show the ad because the ad is returned null and brings direct questions to the screen. How can I do it as I stated. Have a nice day.

my rewarded code

  @override
  void initState() {
    super.initState();
    initRewardedAd();
  }

RewardedAd? rewardedAd;
  void initRewardedAd() {
    RewardedAd.load(
        adUnitId: KAdStrings.rewardedAd1,
        request: const AdRequest(),
        rewardedAdLoadCallback: RewardedAdLoadCallback(
            onAdLoaded: (ad){
              setState(() {
                rewardedAd = ad;
              });
            },
            onAdFailedToLoad:(error ) {
              setState(() {
                rewardedAd = null;
              });
            })
    );
  }

  void _showRewardedAd() {
    if (rewardedAd != null) {
      rewardedAd!.fullScreenContentCallback = FullScreenContentCallback(
        onAdDismissedFullScreenContent: (ad) {
          print('dissmiss');
          ad.dispose();
          initRewardedAd();
        },
        onAdFailedToShowFullScreenContent: (ad, error) {
          print('fail');
          ad.dispose();
          initRewardedAd();
        },
      );
      rewardedAd!.show(
          onUserEarnedReward: (ad, error) {
            print('gosterildi');
          }
      );
    }
  }

```

my onTap to quiz code

```
@override
  Widget build(BuildContext context) {
    return ListView(shrinkWrap: true, children: [
      Column(
        children: [
          ListTile(
            onTap: () {
              _showRewardedAd();
              Get.to(sorubir());
            },
            title: const Text('TEST 1'),
            subtitle: const Text('Soru Sayısı:50, Süre:45 Dakikadır Başarılar'),
          ),
        ],
      )
    ]);
  }
```