Include the Admob ios sdk into your project via cocoapod:
pod 'Google-Mobile-Ads-SDK', "7.31"
GreedyGame SDK has been tested to work correctly with 7.28 to 7.40 of the Google-Mobile-Ads sdk. Support for future versions is experimental.
The minimum Google-Mobile-Ads sdk version supported is 7.28 and the maximum is 7.40.