In some cases, the app may begin showing ads again even though a user has purchased the ad-free version of Thumb Drift. 

This can be resolved by using the Restore Purchases feature in the settings menu of the app. 

For the Android version of Thumb Drift, there is no restore purchases feature as the IAPs are intended to restore automatically as you sign into a Google Play account to which the IAPs have been linked. 

If restoration isn't firing properly on either platform, it is acceptable to use the Remove Ads button a second time - if you had previously made a successful purchase, neither the App store or Google Play will charge you again.