Mac OS could not be installed on your computer
My iMac said that there was an update for my iMac which is running High Sierra. When I installed it, it booted with the following error .....
"The operation couldn't be completed. Undefined error: 0 Quit the installer to restart your computer and try again."
I did so and it boots up to the same screen.
HELP!!!
Please?
iMac 27″, macOS 10.13