Android Studio – Activity is stuck on process dialog and wont go to the next page

So i recently updated my code with the latest admob SDK and dependencies.
it is supposed to show an interstitial ad before going to the next page.
upon running it the StartActivity is stuck on process dialog and wont go to the next page.
here is the code

                //Start Here
                AdRequest adRequest = new AdRequest.Builder().build();

                InterstitialAd.load(StartActivity.this,StartActivity.this.getString(R.string.main_inter), adRequest,
                        new InterstitialAdLoadCallback() {
                            @Override
                            public void onAdLoaded(@NonNull InterstitialAd interstitialAd) {
                                // The mInterstitialAd reference will be null until
                                // an ad is loaded.
                                pd.dismiss();

                                mInterstitialAd = interstitialAd;
                                mInterstitialAd.show(StartActivity.this);
                                mInterstitialAd.setFullScreenContentCallback(new FullScreenContentCallback(){
                                    @Override
                                    public void onAdClicked() {
                                        // Called when a click is recorded for an ad.
                                    }

                                    @Override
                                    public void onAdDismissedFullScreenContent() {
                                        // Called when ad is dismissed.
                                        // Set the ad reference to null so you don't show the ad a second time.

                                        pd.dismiss();
                                        mInterstitialAd = null;
                                        startActivity(new Intent(StartActivity.this, MainActivity.class));
                                        StartActivity.this.finish();
                                    }

                                    @Override
                                    public void onAdFailedToShowFullScreenContent(AdError adError) {
                                        // Called when ad fails to show.
                                        mInterstitialAd = null;
                                    }

                                    @Override
                                    public void onAdImpression() {
                                        // Called when an impression is recorded for an ad.
                                    }

                                    @Override
                                    public void onAdShowedFullScreenContent() {
                                        // Called when ad is shown.
                                    }
                                });
                            }

                            @Override
                            public void onAdFailedToLoad(@NonNull LoadAdError loadAdError) {
                                // Handle the error
                                mInterstitialAd = null;
                            }
                        });
            }
        });


    }
}