This copy of the MacBook Pro Install macOS Monterey application is damaged

Interesting follow up to this, and thanks to @North Hills Guy for mentioning F-secure. I was unable to upgrade to Monterey on my work Mac, a 2019 16" MacBook Pro (Intel Core i9, 16 GB RAM, 1 TB SSD). I received either the 'installer is damaged' error or the 'an error occurred loading the update' error, always about 2 minutes into the install. Trashing and re-downloading the installer did not help. Doing that then booting in Safe Mode and downloading/running the installer did not help. Did not matter if I was on WiFi or Ethernet (via a Stone Pro dock). Booting in Internet Recovery to install the latest OS (Command-Option-R at boot) also failed ('an error occurred loading the update').

My personal Mac is a twin to my work Mac, and had no issues upgrading to Monterey. Nor did my wife's 2020 13" MBP, and I was able to update my kids' MacBook Airs via Internet Recovery (which I did to save having to remove 12 GB worth of data to free up space). Just my work Mac gave this issue.

Although I don't have F-secure, we do use Forticlient for VPN access to the company intranet from offsite. Despite using the VPN Only installer for Forticlient, I did see the occasional requests for permissions that North Hills Guy mentioned, which I had also denied each time.

Long story short, simply quitting the Forticlient app and running the installer did the trick. Honestly, I found this surprising since neither Safe Mode nor even Internet Recovery, neither of which should be affected by a 3rd party app running in the background, enabled me to run the update.

Regardless, I've now got Monterey running successfully on all my Macs.

You could create a bootable installer thumb drive according to this Apple document: How to create a bootable installer for macOS - Apple Support. They work very well.

I had the exact same problem, tried deleting and re-downloading many times. In the end what worked for me was to do the following:

• In the software update dialogue box, click on the More Info in the another update is available section, underneath the install Monterey section:
• 
• In there, I installed the updates to command line for xcode.
• After the update, I restarted my macbook air, then re-downloaded the monterey update. It worked this time...
• Hope this helps!

Just a follow up to this story. When attempting to update to 12.3, I ran into the same problem. In the meantime, I'd been experiencing relatively frequent kernel panics (1-2 times/day) and unexpected app quits. Turns out the problem was hardware, RAM Bank 0 was damaged. So, for those experiencing this issue, it wouldn't hurt to run Apple Diagnostics.

Use Apple Diagnostics to test your Mac

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.

It was called F-Secure. I had tried to remove it and number of times but part of the application files were still present. Occasionally it would throw up a message asking for permissions. I always denied the permission bc I didn’t trust the company. I had to “allow” it finally and Monterrey installed. I then got help totally removing F-Secure.

If you have eliminated interference from anti-virus and VPN and similar software, that leaves this:

If you are having problems with the Sierra / High Sierra / Mojave installer running, with an error reading to the effect of "This copy of the Install macOS Mojave.app application is damaged and can’t be used to install macOS", the signing certificate expired. 

source: http://blog.greggant.com/posts/2018/05/07/definitive-mac-pro-upgrade-guide.html#osupgrades

if trying to install but are not yet running 10.11 El Capitan or later, you likely need to UPGRADE to 10.11 as a waypoint before proceeding

If you downloaded some time ago, a fresh download should have a more recent certificate and yield success.

Choose Applications from the Finder's Go menu, throw the existing installer away, and download another copy.

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<< quitting the Forticlient app and running the installer did the trick. Honestly, I found this surprising since neither Safe Mode nor even Internet Recovery, neither of which should be affected by a 3rd party app running in the background, enabled me to run the update. >>

I don't get how this should be active in Safe Mode or Internet Recovery either, unless there is something privileged or special about communications software that means it DOES get loaded by Safe Mode and/or Recovery.

¿Does this modify the EFI, or something equivalent?

¿could 'having this active' mean that the Installer was always trying to "phone home" using the VPN?

<< I'd boot a Linux Live CD and delete it from there. That has worked perfectly in the past. I do wish Macs had that capability. >>

They do. It's called Internet Recovery (not to be confused with ordinary recovery).

Internet Recovery uses ONLY a small program in the Mac's ROM, and the rest is downloaded from the Internet. it creates about 25 RAM disks for its temporary uses, and leaves your drive COMPLETLY free. (in fact, it does not even require that you HAVE a boot drive to proceed.)

But it only has Terminal available for File manipulation. That should not slow YOU down, if you know command-line.

My nephew fixed mine yesterday. There was a Malware install that was blocking it. We uninstalled the malware and it loaded fine. Check for something along those lines prohibiting the execution of the install.

did you try from Safe mode, which precludes loading of any third-party extensions?

Just to be absolutely certain we are talking about the same thing, the point of Safe Mode is to RUN the Install while still in Safe mode. Inside Safe Mode, no third-party extensions are loaded.

Grant Bennet-Alder wrote:

I don't get how this should be active in Safe Mode or Internet Recovery either, unless there is something privileged or special about communications software that means it DOES get loaded by Safe Mode and/or Recovery.

¿Does this modify the EFI, or something equivalent?

¿could 'having this active' mean that the Installer was always trying to "phone home" using the VPN?

Agree, very odd. I have had prior issues with MacOS upgrades on company-managed Macs when the update was performed offsite (which became an issue with the onset of COVID). In fact, I got locked out of a prior company-provided 15" MBP with the Big Sur update I suspect due to Centrify password management, they had to wipe the machine. However, this work Mac isn't enrolled in any sort of MDM. I had no issues with incremental updates, and this one shipped with Big Sur so this was the first major upgrade.

I'll just remember to quit Forticlient before running the MacOS 13 update (or will it be 14?).

I have the same issue on my MAC 15" Late 2016. I'm currently running Catalina but Monterey say's the installer is damaged. I've trashed it 3 times from applications but say's its damaged on every new download. What is up?