Late 2015 iMac with Monterey Start Up Problem

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Late 2015 iMac with Monterey Start Up Problem

I need help with my late 2015 IMAC with Monterey. I get to Home Screen. Apple logo and Log in screen comes up. After entering password the screen goes blank for a couple of minutes and then says it restarted because of a problem and then goes back to the login screen where the same thing continues to happen. Note that I have not changed my password and have done nothing out of the ordinary recently. Steps taken so far (multiple times):

Recovery mode-all volumes found to be good.

Could not restore from Time Machine

Tried to reinstall Monterey and it says build info.pre-flight.error.error 21. Both Ignore and Report links do not work

Safe Mode: Screen is black

Detail:HD Volumes Capacity2.12 TB, Available:752.85 GB Used 1.36 TB. Base System Capacity Read Only 1.14 GB Available 128.6 MB. Used 920.8 MB

Question: Obviously I cannot Access Time Machine or Files for my data recovery. I recently turned off ICloud. Would turning off I cloud be part of this problem? Is there a way to access Time Machine to recover files if I can’t get on to my desktop? Importantly. Am I doomed to lose everything and have to buy a new computer?

Thank you for any advice.

Posted on Dec 2, 2025 12:35 PM

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Answer 1

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John Galt

Level 10

155,060 points

Dec 2, 2025 1:01 PM in response to Jmellio

The Mac is exhibiting a kernel panic upon logging in: If your Mac restarts and a message appears - Apple Support

Press and hold a Shift key immediately upon logging in. Release the Shift key only after a Finder window opens, or it crashes again. That action will prevent loading of any Login Items that may be contributing to the KP events.

Boot macOS Internet Recovery mode and reinstall macOS. To force the Internet Recovery version to load, add an option key to the ⌘ R startup key chord, details explained under If you can’t start up from macOS Recovery (Intel-based Mac) here: How to start up from macOS Recovery - Apple Support

Should you get as far as restoring a TM backup, iCloud is definitely not a factor. Should it come to it, you can migrate its contents to a replacement Mac.

Safe Mode: Screen is black

That's not a good sign. It suggests a hardware problem, as does the failure to reinstall Monterey. A repair, if one is even possible for such an old Mac, is likely to be economically unjustified.

Try macOS Internet Recovery before giving up on that Mac, or pursuing a possibly expensive repair.

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