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Unable to update macOS

iMac came preloaded with Big Sur & updated to Monterey last fall. Started noticing Hash Mismatch errors a little bit after this. First Aid saw error & could not fix. Did a backup, erased & tried reinstalling Monterey "error occurred" every time. Did a Time Machine recovery to around time when Montery was installed , & this seemed to work to at least get me going. Tried to update to 12.3.1 now this failed to update. Did clean install of Monterey " Error Occurred" every time even Safe Mode, resetting Ram . Same senario with a Big Sur installer. Only way I can get a OS on the Mac is with Internet Recovery and having Catalina OS. Tried update for Monterey and no go. This is a 250GB SSD HD


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iMac 21.5″, macOS 10.15

Posted on Apr 14, 2022 3:09 AM

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Posted on Apr 14, 2022 5:29 AM

At this stage considering all you've done and the problems you're having, talking to Apple seems to be in order: Mac Repair - Official Apple Support


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8 replies

Apr 14, 2022 6:45 AM in response to toolman1818

Follow the previous advise and have the computer evaluated by Apple or Apple Authorized Service Centre.


Have them do an Over Nite Test with their Special Hardware / Software and make specific to mention to check the RAM Modules for possible Module Failure.


Have seen another couple of people with this exact same issue and presto - RAM Module failed the Stress Test.

Apr 14, 2022 9:37 AM in response to toolman1818

Any After Market Drive in the 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 same would apply if the user is attempting to instal Monterey to an External 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.

Unable to update macOS

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