Users running macOS Mojave and older operating systems have experienced issues accessing the App Store and its content.
Error messages pop up whenever users try to download or sign into the App Store, including ‘the data could not be read because it isn’t in the correct format’, and ‘an unexpected error occurred while signing in’. The results vary depending on the operating system, with Sierra 10.12 users not having access, High Sierra users having failed sign-ins and missing interface elements, and Mojave users being able to browse but unable to download or purchase apps. Those running Catalina 10.15 have not experienced these App Store problems.
It’s said that the issue is tied to recent Mac App Store changes and how the platform handles receipts. However, Apple has not issued a formal statement or announcement for the errors. macOS installers can be found through the developer websites.
