Mac App Store Stops Working on Older macOS Versions

Mac users running macOS Mojave (10.14) and earlier versions are reporting widespread issues accessing the Mac App Store, with many unable to sign in or download previously purchased apps.

Based on reports compiled by Michael Tsai, the problems appear to have emerged around January 24, 2025, coinciding with Apple making changes to Mac App Store receipts. Users attempting to access the store on affected systems are receiving various error messages, including "An unexpected error occurred while signing in" and "The data couldn't be read because it isn't in the correct format."

Different behaviors have been reported across affected macOS versions. Catalina (10.15) and later versions continue to function normally, while users on Mojave (10.14) can browse the store but are unable to complete new purchases or download previous purchases once their current session expires. Meanwhile, High Sierra (10.13) users are reporting missing interface elements and failed sign-in attempts, and Sierra (10.12) users are encountering error messages preventing access.

The timing suggests a possible connection to Apple's recent changes in Mac App Store receipt handling, but the exact cause remains unclear. For users affected by these issues, Apple provides alternative sources for macOS installers, and many third-party apps remain available outside Apple's App Store ecosystem via direct downloads from developers' websites.