Monterey Installer app fails preparing installation

That's what I am doing. You have to create a bootable Monterey USB installation drive. Do a search for a video on how to do that. You'll need a 16GB USB drive (or bigger) do this. I actually am using an old spare 60GB hard drive in a USB enclosure for that. Then boot into the boot menu by holding down the Option key while it reboots. Then load the installer and have it install it on your original SSD in the USB enclosure. Then when it's done it you should be able to unplug that drive and then install Monterey on your new SSD.

Well from what I read we should be able to install Monterey on this drive. I have the same drive as you., but when I tried this last night, something didn't go right and it didn't install on the drive like I've seen in videos I've searched on. I am going to try it again and I will put the steps to do it on here if it works. If it doesn't work, I need to take apart the machine and install the old drive back into it and try that. I don't have the pentalobe screwdriver to remove the back off of it with me right now.

I could never get it to install on my old SSD with it in the USB enclosure for some reason. It would get to where it would start the install showing X minutes remaining but then would stop and restart into the recovery mode. So I had to open up my laptop, install the old drive, install Monterey using the usb install disk I made, ensure the firmware had upgraded to the necessary version needed to install on my new SSD, then I reinstalled the new SSD back in the laptop and installed Monterey using the downloaded installer from the App Store. Sure is a long workaround but seems to have worked fine and Monterey is running on my OWC drive now.

Just a bit of feedback. I have an OWC SSD in my Mac Pro, and fortunately still had the original Apple SSD in a USB housing. I contacted OWC to see if they could help. They confirmed that re-installing the original Apple SSD and installing Monterey would fix the problem, as installing the new OS updates some sort of BIOS in the Mac Pro which then allows the OWC SSD to be upgraded to Monterey.

It was a bit of a pain to do. But quite straightforward. I made sure my Mac had a good Backup then created a bootable USB Stick with the Monterey Installer (instructions on Apple's website). I reinstalled the Apple SSD in my Mac Pro and upgraded it to Monterey by starting up from the bootable USB stick. I then replaced the OWC SSD in my Mac, and did a fresh install of Monterey from the bootable USB Stick (thought it was a good opportunity to do a fresh install rather than an upgrade), before re-syncronizing my iCloud content and re-installing applications and the like.

All this took about an afternoon of messing around, but definitely worth it as I'm now running the latest OS (which I hope will upgrade more easily in the future) and my Mac Pro feels much snappier than it did before the OS upgrade.

To be clear, macOS Monterey will not install if you have upgraded your SSD? What does it matter what SSD I'm using - is this a macOS upgrade or just a way for Apple to ensure I'm using their overpriced hardware?

I believe Apple owes us a better answer than - find your old SSD, reinstall it, upgrade that OS, and then port the newly upgraded OS and your data back over to the new SSD you installed because the old SSD was running out of space.

Come on Apple, you have to do a lot better than that.

This seems like an awful lot of trouble to upgrade. I agree. Am I going to have to tear my machine apart, bypass the flaw and reinstall every time there is an upgrade now? What changed? You're going to have to come up with a better explanation other than I'm not using an OEM SSD drive. Apple folks are fairly savvy. I'm sure we could understand your explanation. This doesn't seem hardware related and it certainly not right.

It’s not so much a hardware issue rather than a firmware issue. Once the firmware is installed, which can only be done with an OEM SSD for some reason, Monterey can be installed on the 3rd party SSD. In the future if a different firmware is needed to install an new OS version the OEM SSD will probably have to be put back in and this process done all over.

You don’t have to port your data over to the new SSD. Once the firmware is updated to the version it needs to install Monterey you just run the installer on your new SSD that has whatever previous version of OSX you are running. No need to do a fresh install unless you want to.

There appear to be two instances of installer failure included in this thread. One appears to be, more or less, "solved," in that those with aftermarket internal drives as replacements for failed hardware or upgrades need to go through some gymnastics to fool the installer into seeing Apple hardware to allow the firmware upgrade and subsequent OS install to run. Then there is MY problem, and at least two others in this thread, where the installer fails to run on relatively new (2017, in my case), factory OEM hardware. In my case, the "... firmware update..." popup ALSO shows up. This seems to be a smaller group, so far. Should I start another thread?

Yep. Big Sur 11.6.1. I was a bit surprised also. The Monterey installer actually worked fine on my 2015 13-inch Macbook Pro, a much older machine that I figured might run into some issues. It also worked fine on my wife's 2019 iMac. I was even more surprised I was able to install Monterey on an external OWC SSD, and get it to run with no problems. I've read only a few other posters on the Apple Support Forum who have run into this problem on a factory-standard machine. So far, it seems none have actually solved the problem.

This is a BS issue. Its ridiculous for Apple to put out an upgrade for dedicated Apple users and not have it just do the simple task of upgrading the OS. I replaced my original 500GB SSD from my mid2015 MacBook Pro with a 2TB Fledging M13 SSD. It has worked perfect and kept my MacBook in top shape. I sold my original SSD drive due to the fact that during the time I have been using my M13 SSD One, I did not need it and Two, my MacBook upgrade to the last two upgrades with no issues at all. So why now change the game!!! Come on Apple fix your software so that everyone doesn't have to change SSD drives to get the upgrade! I will just keep using Big Sur until.

I just wanted to update my eventual solution. I could not get the new drive unscrewed from the machine so had to take it to be installed. Luckily, the Onyx Consulting people are really nice people, it only took and hour to do.

Thank you you for all the help!

I submitted a bug report today:

https://feedbackassistant.apple.com/feedback/9787896

I read you have to turn off your firewall and or VPN before installing.

What do you do if you don't have the original Apple drive anymore? I have a 2013(late) MP which is getting the same error.

Any suggestions?