There might be several causes on why the reward couldn’t be granted. To be sure that everything in your way is fine, follow these steps:

• Be sure to have a stable internet connection before starting to watch Ads.
• Watch the ads long enough. When you see the “X” or the “>>” Icon in one of the corners of the game, it means that you have watched the ad long enough. Tap on these icons to close the commercial properly and get your reward.
  Mind that sometimes you have to press several times in different closing icons.
• Do not use the “Back” Button from your device to close the Ad.
• When downloading an application from an Ad, don’t spend too much time outside Merge Mansion.