High Sierra Upgrade fails with: An error occurred while verifying firmware
I've tried a number of times to upgrade my iMac 2011 21.5" to High Sierra and each time it fails with the message:
macOS could not be installed on your computer
An error occurred while verifying firmware
My machine was "fixed" by Apple about 10 months ago after a failed disk drive. It was a dual "fusion" drive with 1TB HDD and 128 GB SSD. Now is the same. Has loads of free space and seems to work well.
iMac (21.5-inch, Late 2012), macOS Sierra (10.12), null