Won't boot afther upgrade to macOS Sierra

Try to press and hold Command-Option-P-R on bootup until you see or hear something new. Also, do you have another Mac that is new enough to download macOS Sierra from the App Store? If so, you can use target disk mode to install macOS onto the iMac via another Mac.

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3 Comments:

Oke thnx for you answer.

I will try the target disk mode.

That is the only thing i didn't try jet .

The Judge

Nov 25, 2016 by The Judge

Target Mode did the Job

I did have to reinstall OS X but that's oke

Thanks for the tip

Nov 28, 2016 by The Judge

@thejudge Glad to hear that :) No problem!

Dec 1, 2016 by Ben

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Oke thnx for you answer.

I will try the target disk mode.

That is the only thing i didn't try jet .

The Judge — The Judge
Target Mode did the Job

I did have to reinstall OS X but that's oke

Thanks for the tip — The Judge

Dan @danj Rep: 478.8k Self employed contract worker 35 329 970 · Answer 1 · 2016-11-22T05:12:02-07:00

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Dan @danj

Rep: 478.8k

Self employed contract worker

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Posted: Nov 22, 2016

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Your system maybe just fine!

Apple requires a full restart during the upgrade process a few times as the there is a firmware update as well as an OS update (I've had systems do four restarts to apply everything).

The other problem I've seen is a HD which has problems go into a tailspin of restarts as the firmware update is not able to complete. The only way to overcome this is to boot up under an external drive or use a second Mac system to fix if possible your drive using Disk Utility by putting your system in Target Mode. Otherwise you may need a new drive.