If the App Store method is failing or you are on a newer Mac, these community-trusted tools can help you fetch the installer directly from Apple's servers:
To download macOS High Sierra as a or installer file, it is recommended to use official Apple sources or specialized tools that fetch the installer directly from Apple's servers. Official Download Methods Mac App Store (Direct Link) : You can find macOS High Sierra on the App Store macos high sierra 10.13.1 dmg
6 full installer. ... You need to open this page in Safari. The download link will not work from Firefox. Apple Support Community Download macOS High Sierra 10.13.2 - Apple Support If the App Store method is failing or
2GB RAM minimum (8GB recommended for modern performance). macos high sierra 10.13.1 dmg