You can optionally enable logging by using the enableLogging method. If an impression wasn't registered, a message appears in the console.

Invalid integration indicator for native ads

If an error was made when integrating native ads, an indicator appears on top of the ad in simulator mode. Click on the indicator to see a message with debugging information to help you understand the reason for the error. Click the indicator again to hide the message.

By default, the indicator is only shown in simulator mode (device type YMADeviceTypeSimulator). You can view device types in YMADeviceType.

To enable the indicator for real devices as well, pass the value YMADeviceTypeHardware | YMADeviceTypeSimulator in the enableVisibilityErrorIndicatorFordevicetype: method:
[YMAMobileAds enableVisibilityErrorIndicatorForDeviceType:YMADeviceTypeHardware | YMADeviceTypeSimulator]
To turn off the indicator, pass the value YMADeviceTypeNone in the enableVisibilityErrorIndicatorForDeviceType: method:
[YMAMobileAds enableVisibilityErrorIndicatorForDeviceType:YMADeviceTypeNone]