Can't I upgrade my 2020 iMac with macOS Monterey to a higher system

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Level 1

21 points

Can't I upgrade my 2020 iMac with macOS Monterey to a higher system

I have a 2020 iMac which came to me 2nd hand with os x Monterey. I am unable upgrade to anything above (I'd like Sonoma but I tried the system below Sonoma But I keep getting the message "This iMac does not suppport the system you are trying to install. I've even tried deleting the System / Upgrade file but it does not allow this. I even tried erasing the hard drive and doing a clean system install.

Could perhaps the fact that I am using FUSION HD impact this? Apparently, there is a 250GB SSD where apparently the System resides and a 2 Terabyte "data file".

Help. I've tried everything including TechTool Pro to wipe both drives. It's driving me crazy. I even looked upthe serialnumber to confirm it is a 2020 iMac. It is, apparently.

[Re-Titled by Moderator]

Original Title: I HAVE A 2020 iMAC WITH O X MONTEREY, WHY CAN'T I UPGRADE TO A HIGHER SYSTEM?

iMac 27″, macOS 12.7

Posted on Feb 14, 2026 10:02 PM

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Answer 1

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curtispsf Author

Level 1

21 points

Feb 15, 2026 5:42 PM in response to curtispsf

I have tried every conceivable way of trying to update. Finally, I called Apple support. It took 2 hand offs before I reached Top Tier support. After 30 minutes trying various things, she reported that it probably was a 2015 iMac, no a 2020. We compared the memory installed 32gb of DDR3 memory against what should have been for a 2020 iMac [DDR4]. The DDR3 is linkedto a 2014/2015 iMac. She thought thatmaybe they took a Logic Board from a 2020 and put it in a 2014/2015 to get "about this mac" to think it was a 2020 machine with specs for 2020. Even. the serial # matches that of a 2020 iMac. Also, Apple has some proprietary software she ran against my computer and it indicated this to be a 2015. I bought this on ebay with a seller nolonger listed on ebay. WESELLMACS Now i see other screennames such as ISELLMACS. The lesson: be very wary dealing with refurbishers. You are better off buying a computer from an INDIVIDUAL with good ratings who has a single machine to sell. FRAUD ABOUNDS. I am waiting to heAR from ebay if it can trace the name of the individual who sold this tome to another existing ebay account. Thanks for ALL your feedback to everyone who replied to my post. I appreciate it!

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Answer 2

MartinR

Level 7

25,165 points

Feb 15, 2026 7:42 AM in response to curtispsf

The 2020 iMac models are compatible with macOS Sonoma & Sequoia. And even Tahoe. Are you absolutely sure you have a 2020 model? Look in Apple > About This Mac for the model descriptor:

Having a Fusion drive doesn't make any difference. The Fusion SSD & HDD are combined into a single logical drive and it has nothing to do with whether or not you can install a particular version of macOS.

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Answer 3

Feb 15, 2026 2:34 PM in response to curtispsf

I think I would try and Start up your Mac in safe mode. and then while in safe mode, attempt to apply the upgrade.

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Answer 4

MartinR

Level 7

25,165 points

Feb 15, 2026 1:55 PM in response to curtispsf

curtispsf wrote:

I have a 2020 iMac which came to me 2nd hand with os x Monterey. I am unable upgrade to anything above (I'd like Sonoma but I tried the system below Sonoma But I keep getting the message "This iMac does not suppport the system you are trying to install.

Was this Mac already installed when you got it and did it have any existing user accounts on it? If it had any existing user accounts on it, was there more than 1 admin account?

How did you attempt to upgrade to Sonoma? Software Update? Download from the App Store? Bootable installer? At what point did you get the error message ""This iMac does not suppport the system you are trying to install?"

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Answer 5

curtispsf Author

Level 1

21 points

Feb 16, 2026 2:04 AM in response to MartinR

Yes, I absolutely checked atm [about this mac]. It says that I have a 2020 imac 5k, 27"; 4 GHZ QUAD-Core Intel Core 17. I thought perhaps this was an earlier model which had been flashed to a 2020 iMac, but I checked the serial # with Everymac's lookup tool and it is what it says it is,

I even used Onyx to reveal hidden folders and trie to change permissions so I could permission to delete the /Library/Updates files but not allowed to fo this.

I am at wits ed trying to make this update as it should.

Any ideas? Thanks !

[Edited by Moderator]

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Answer 6

Feb 16, 2026 7:42 AM in response to curtispsf

Thank you for sharing this update with the Community.

It's unfortunate that you find yourself in this unusual situation, but sharing it provides something for us all to consider when looking to buy a used Mac.

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Answer 7

Feb 16, 2026 9:56 AM in response to curtispsf

curtispsf wrote:

The lesson: be very wary dealing with refurbishers. You are better off buying a computer from an INDIVIDUAL with good ratings who has a single machine to sell. FRAUD ABOUNDS.

If you're looking to buy a used Mac, you may want to avoid eBay, etc. in favor of buying from

Apple (Refurbished Mac Deals - Apple)
Other World Computing (Other World Computing – New & Used Macs)

Apple appears to have the better refurbishment process. Other World Computing appears to have more selection (if you are looking for an older Mac).

Note that a seller / previous owner should do this:

What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

If they don't, you may run into problems, especially with Apple Silicon Macs, or late-era Intel Macs with T2 security chips, which support Activation Lock.

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