"Failed to personalise the software update" on macOS 27 Golden Gate Beta

I failed to install macOS 27 Golden Gate Beta despite trying several times.

The 17GB update downloads successfully, but the installation fails with either:

  • “Failed to prepare the software update. Please check your internet connection”
  • “Failed to personalise the software update”

My network connection is fine, and I have around 110GB of available storage. So far, I’ve tried:

  • Downloading the update again several times
  • Fetching the full installer with softwareupdate --fetch-full-installer
  • Running startosinstall
  • Verifying date and time settings
  • Removing Keychain certificates
  • Running sudo nvram -d ota-restorekernel
  • Waiting and retrying the installation later

I’m using an M4 MacBook Air registered in the Beta program. Has anyone encountered the same problem or found a working fix?