Rebuilding the app will not change things. If you check event.info you’ll see the reason for why it failed. The main reason for ads not being shown is when the inventory for your device has been depleted. In that case the listener will return a response of ‘failed’ with event.info set to ‘no ad found’. Video ads can be very scarce.
It’s not recommended to test your app with real ads, as there’s no guarantee for 100% fillrate. It’s better to have Test Mode activated during testing. If test ads show (which should be 100% fillrate in Test Mode), then you can be assured everything is working.