Reward Ads and Microtransactions for Finished Mobile Game

We have a completed mobile game ready for launch, on Android and iOS. It was made with Unreal 4, and runs flawlessly on Android. However, reward ads and microtransactions cause iOS to crash, or at least stall the game indefinitely. We are looking for someone who has experience with reward ads and microtransactions, as well as an ability to program with C++. Unreal experience is definitely a plus, but not necessary if your are proficient with C++. We just need this issue fixed so we can release the game. We have had trouble finding someone who has the specific skills for the job, and are hopeful we can find that person here.