Upgrade for current EtreCheck users
The App Store version of EtreCheck is only for new users. Apple’s App Store is a closed environment and run according to Apple’s strict rules. Apple does not allow external licenses or purchases to be moved into the App Store.
Existing, licensed users of EtreCheck should download EtreCheckPro. It is a free and seamless upgrade from EtreCheck 4. It is more powerful than the App Store version and will probably always remain so. Your EtreCheck 4 license should automatically enable the Power User package in EtreCheck 5.