high sierra firmware error

Hi, I try to upgrade to High Sierra from Sierra and I got "... an error occurred while verifying firmware". I have read couple of posts, but no one helped.

I have iMac 21,5 mid 2011, Boot ROM ver. IM121.0047.B23, SMC ver. 1.71f22, Journaled HFS+ HDD WDC 1TB (not original apple HDD). HS Installer is 5,23GB from 29 June 2018 from Appstore, it starts the HSierra installer, restarts one, showing apple loading, showing 45 minutes to finish install, do a restart, machine long BEEP, 4 times like ON/OFF switching, restart with showing apple loading, then error msg.

I checked the HDD for errors with Diskutil, no errors, I tried to do it also in safe mode, result is the same error.

Hope someone can help.

Txs!

iMac 21.5", macOS 10.12

Posted on Nov 20, 2019 1:05 AM

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dot.com

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2,455 points

Posted on Nov 20, 2019 9:06 AM

That's a very old High Sierra installer and think it might have an expired installation certificate. Download a current version that should be available at https://support.apple.com/en-us/HT208969

Good luck...

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high sierra firmware error

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