Attempted to update OS. I waited 24 hrs to power it off after it hung up with one minute remaining to finish the update. The screen shows a yellow warning symbol above an option to either select Startup Disk or Update. The Restart option simply refreshes the page. The Startup Disk option only shows Macintosh HD 14.7.4, and when I select it, the warning symbol appears again. Please advise. Thanks in advance.
[Re-Titled by Moderator]
Download it on another Mac through this Apple official link Sonoma 14 or download a Sonoma installer from the internet (I personally don't recommend trying download it from the internet, because the source can be insecure) and make a bootable drive (like a pen): Create a bootable installer for macOS - Apple Support. If this don't work, consider restoring the Mac with a Time Machine backup or installing an older version of macOS and then update to Sonoma (recommendation: in your case, attending the hardware you have, I would suggest you to enter Internet Recovery Mode - command+option+R - to install macOS Sequoia.
See this Apple article for various startup screens you may see:
If your Mac doesn't start up all the way - Apple Support
Specifically for the screen you are seeing:
How to start up from macOS Recovery - Apple Support
It means the current update can't be installed due to some hardware issue. Please force restart and check if it goes to desktop.
For me it helped going into Disc Utility and do a disc heck and repair.
macOS update stuck with yellow warning symbol
