I have Big Sur 11.6.5 and have tried 3 times to install the latest Monterey on my iMac which is compatible(late 2015) and has enough storage space(900+ GB). The installation appears to be going well showing how many minutes remaining. However after the computer restarts and logging on, I click on About This Mac, it's still showing Big Sur. Wondering what's going on.
Thank you,
iMac 27″, macOS 11.6
EDITED - Corrections
Firstly Big Sir 11.6.5 as of Monday May 16, 2022 has had an update available to version 11.6.6
Secondly and only the user knows if this applies to this machine.
There are reports appearing on the ASC Forums regarding failed installation of Monterey on older Qualifying Apple Computers.
In most cases this is related to having a NON Apple Original Internal Drive ?
The EFI Boot ROM included in Monterey is verifying for Original Apple Drive and if not found , may Balk or fail to upgrade to Monterey.
Reports indicate the EFI BOOT ROM is Required to Flash the Computer and is a requirement for a Successful Monterey Installation.
If above does apply - the only solution is reverse back to Original Apple Drive - run the Monterey Installer to that Drive.
Then, reverse back to After Market Drive and again run the Monterey Installer to that drive.
EDITED - Corrections
Firstly Big Sir 11.6.5 as of Monday May 16, 2022 has had an update available to version 11.6.6
Secondly and only the user knows if this applies to this machine.
There are reports appearing on the ASC Forums regarding failed installation of Monterey on older Qualifying Apple Computers.
In most cases this is related to having a NON Apple Original Internal Drive ?
The EFI Boot ROM included in Monterey is verifying for Original Apple Drive and if not found , may Balk or fail to upgrade to Monterey.
Reports indicate the EFI BOOT ROM is Required to Flash the Computer and is a requirement for a Successful Monterey Installation.
If above does apply - the only solution is reverse back to Original Apple Drive - run the Monterey Installer to that Drive.
Then, reverse back to After Market Drive and again run the Monterey Installer to that drive.
Thank you Luis,
Your suggestion worked :-)
Try doing the installation while running in Safe Mode.
Monterey won't install
