The reported error commonly derives from not having your Android SDK up to date. This has been confirmed at Unity Answers and Stack Overflow.
Updating your Android SDK to at least API level 21 (also known as Lollipop) should fix your problem. Regardless, it is a good idea to ensure you have the latest version of the Android SDK.
Further confirmation at Unity Answers implies that Unity should have detected this problem, and automatically attempted to upgrade your SDK. The fact that it does not implies the presence of a bug, which you may consider reporting
Contrary to the other answer, you do not need to specifically target the API, in your build. isGame
and banner
are both members of the application declaration. The application declaration has an API requirement of API Level 1 - it has always been there.
As such, versions that pre-date Lollipop will not freak out over newer inclusions; they just wont use them.
No resource identifier found for attribute 'isGame'
returns answers.unity3d.com/questions/914949/… \$\endgroup\$