Are you using a to create the installer?
Finding a legitimate DMG (Disk Image) for High Sierra is surprisingly difficult. Apple officially distributes macOS installers through the as .app files, not DMGs. This creates a gap that users often try to fill by searching for third-party DMG links. download macos high sierra 1013 6 dmg file link
If you are on Windows or cannot access the App Store, these reputable repositories host full DMG/ISO images: Are you using a to create the installer
curl -O http://updates-http.cdn-apple.com/2019/cert/061-39476-20180921-788c1f11-45e1-4693-a69d-0144a4ae18b3/InstallAssistant_highsierra.dmg unmodified installer wrapper.
The link provided below is the link for the final version 10.13.6 (17G66). This is a digitally signed, unmodified installer wrapper.
