Why does the app say it cannot verify license?
To prevent piracy, the app checks online whether the copy you have installed has been legally purchased from the Play Store with the Google account you are using. The check is made the first time you start the app so it's necessary that you are online the first time you start the app. The check is also made later (basically every time you start the app) but the app can be started several times without successful license verification so you don't have to be online every time you want to use the app.
When you get this message, please make sure you are connected to the Internet and try to start the app again or press the "Re-Check" button. Also make sure that you are using the same Google account that was used to purchase the app - the app won't run when you change to another account.
The check is made using Google libraries and services so make sure you did not disable access of these services to the Internet (these are services like Google Play Services, Play Store, etc.).
If you tried to copy the apk file from some other web site than the Play Store or you copied the apk from your friend's phone, you are out of luck - the app won't work unless you purchase a legal copy from the Play Store.