I’m trying to display interstitial add on a button tap in my flutter based application, ad loaded as well but when I try to show it, it notifies the following callback onAdFailedToShowFullScreenContent and throws following error

error(code: 17, domain: com.google.admob, message: the provided view controller is not being presented.) site:stackoverflow.com

here is the code

this code opens up the showModalBottomSheet

  void show() {
    showModalBottomSheet(
        context: context,
        constraints: const BoxConstraints(
          maxWidth: double.infinity,
        ),
        builder: (context) {
          return AudioConverter();
        });
  }

class _AudioConverterState extends State<AudioConverter> {

@override
Widget build(BuildContext context){

return Container(); // there is a button inside it, on the tap of that button, it calls the displayAd() function
}
}

displayAd function

  void displayAd() async {
    if (interstitialAd != null) {
      interstitialAd!.fullScreenContentCallback =
          FullScreenContentCallback(onAdDismissedFullScreenContent: (ad) {
        convert();
      }, onAdFailedToShowFullScreenContent: (ad, adError) {
        print(adError); // the provided view controller is not being presented
      });
      interstitialAd!.show();
    } 
  }