chartboost ad shows up just once on android

Hi all, I am trying to integrate chartboost in my android unity project. It did work perfectly fine earlier. But suddenly following problem began on android. Ads appear only once on android & doesn't show up again at all. Even with new build and in test mode too. Its working fine on ios with similar settings and code.

Have used following code in chartboostexample: (Gameoverbool shows ad only on game over screen) void Update() { Chartboost.cacheInterstitial (CBLocation.Default); if (Chartboost.hasInterstitial (CBLocation.Default) && !onceAd && DymoCream.gameOverBool == true ) { Chartboost.showInterstitial (CBLocation.Default); onceAd = true ; } }

Would appreciate any help. I am new to unity so may be I am missing something here. I have tried to find similar threads too but these are unanswered.

Android Mainfest file: https://www.dropbox.com/s/w3cln1ccfkn6axl/AndroidManifest.xml?dl=0