An error occurred while updating the firmware time capsule who is somaya reece dating from terror squad
Because the APFS requires support of new version firmware, your mac's firmware will be updated to latest version during the installation of High Sierra if it hasn't got one.
After the first restart, the installer prepares the latest version firmware which suitable for your mac model onto EFI system partition of your main disk with command.
Make sure you delete any existing installer you might have first.In my case, I expect the firmware checker was expecting a HDD in this machine when it's now an SSD.Apple has introduced a new file system APFS in High Sierra.The great thing is the Airport Express offers you incredible flexibility due its portability.I know with mine I get a pretty good signal without it but with it, I can put it out on the back patio and enjoy streaming music. If you are trying to extend a wireless network that is not an Apple Airport base station it cannot be done.