XCode: All versions | Appodeal SDK: All versions

AdColony always checks if the key window’s rootViewController matches the passed rootViewController. Otherwise, Adcolony fails to show the ad. If your app has multiple independent windows, you can get a message with this or similar text:

AdColony [*** ERROR ***] : AdColony has ads, but could not display them. AdColony was unable to find the currently visible UIViewController for your app. Please ensure that your key UIWindow has a rootViewController.

It means that the rootViewController that was used in showAd doesn't belong to the first window in the array.