macOS Monterey Update Failed

Welcome to the Apple Support Communities.

Try these steps:

1. Drag the "Install macOS Monterey" App to the Trash & Empty the Trash.
2. Startup in Safe Mode, login, and restart into normal mode.
3. Follow these steps: How to upgrade to macOS Monterey - Apple Support.

Jack

I've had better luck from the Safe Mode because I evidently have some 3rd party software that interferes with the installation so try the following:

#1 - boot into Safe Mode according to Start up your Mac in safe mode - Apple Support.

NOTE: Safe Mode boot can take up to 3-5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

#2 - go to the System/Software Update preference pane and begin the download.

#3 - run the installer from the Safe Mode.

ACE_TANG wrote:

Cannot Update the macOS from Big Sur v11.6.1 to Monterey.

The operation couldn’t be completed. (PKDownloadError error 3.)

Uninstall the macOS Monterey download file and Retry, the Error is still again.

https://discussions.apple.com/content/attachment/96cbf64b-2ad6-4c6c-a671-2822ca6e5a05

I would simple try back at a later time, a later day and compare your results.

The servers are being slammed as the macOS rolls out.

I received that error once when I tried to install on external drive. Problem was that I had replaced the internal Apple SSD with a standard NVMe drive on my 2013 MacPro. I got different error when I tried to install on the internal NVMe drive. Solution was to reinstall the original Apple SSD internally and upgrade that SSD to Monterey and then I could update the NVMe drive that I installed in and USB enclosure.

Question, do you have the original SSD installed in you Mac. I previously asked for model and year of your Mac.

For some Macs, the Monterey update includes updating the Mac's firmware and for that the installer checks to see if the internal Apple is installed. If not the install terminates.

Where would you find the Install macOS Monterey app? I've downloaded Monterey several times onto a new MacMini and after it appears to have downloaded everything, it sits for about 5 minutes then shows the following error message:

I don't find an install app for Monterey anywhere so I can't delete it. It's definitely not in the Applications folder or anywhere else that I can find. I've done a search for "monterey" with no results returned. I did have the download itself fail a few times because of a dropped connection, but today it seemed to get the full file but failed on installation.

Any other suggestions would be appreciated.

When fully downloaded, a macOS installer is in the applications folder titled: Install macOS Monterey.

Sinc you say it is not there it would seem that it never fully downloaded. After it looks like it is download some things are done to the file before it is ready to use.

Are you using a wifi connection? If you dropped that before can you use a wired connection?

Do you have another Mac that can run Monterey? If so you can download the Monterey installer on that Mac and move it to this Mac.

I do have a MacBook Air on which I was successfully able to download and install Monterey. How can I download the Monterey installer without it automatically trying to reinstall it? When I go through the App Store to download it, it takes me to the Software Update screen in System Preferences and asks if I really want to download Monterey. I'm concerned that if I say yes it will download it and then go ahead and try to reinstall it, not giving me the chance to grab the installation file I need for the Mac Mini. Will it indeed stop after the download so I can get the installer file? Since I don't see the installer file on the MacBook that is already running Monterey, I assume it automatically gets rid of it after installation. I even looked in the trash on the MacBook, but don't see the installer file in the trash so it must REALLY get rid of it.

Thanks.

What model/year Mac?

I have got an iMac (Retina 5k, 27-inch, Later 2014), Can I upgrade to macOS Monterey

I tried running the upgrade while in Safe mode, but had the same result. It failed with the same error message as I originally posted.