We have recently changed from a paid app to a freemium app where users are free to try the app and then unlock the version should they need to.
This means that anyone updating to version 3.0 and above for the first time will face this message most probably. BUT you DO NOT have to pay again for the app.
The steps to unlock the full version if you have bought the app before is to follow the simple steps below:
In the unlikely event this does not happen automatically, please press the settings page in the app. and click on the restore button. It might ask you to sign in again and will then unlock the app.
If all those steps above does not solve your issue, please contact us at firstname.lastname@example.org and we will sort it out for you as soon as possible.