If you purchased the game at some point, there is no need to purchase it again!

To restore a purchase of the ad-free version, access your Mahjong game and tap the game screen to raise the Menu bar, select the Options tab and at the bottom, select Restore Purchases.

If this method does not work, we recommend checking your App Store account purchase history and be sure to sign in with your original Apple ID. From your purchase history, you will be able to restore the game by downloading it if it is not already installed on your device. Check your purchase history through this link.