| Error Code | Description | Resolution | | :--- | :--- | :--- | | | Expired certificate (Apple stopped signing 10.13.6 installer certificates in 2023). | Set system date to 2019 before running: date 010100002019 in Terminal. | | "macOS could not be installed" | Firmware mismatch or APFS conversion failure. | Ensure target Mac supports APFS (SSD required for bootable 10.13.6 on some HDDs). | | Download stuck at 2.1 GB | App Store cache corruption. | Clear App Store cache: rm -rf $TMPDIR/../C/com.apple.appstore/ |
Version 10.13.6 was the final stable release for High Sierra, introducing several foundational improvements: Download macOS High Sierra 10.13.6 Update - Apple Support high sierra 10.13.6 download