Why is my MacBook Air stuck on update for 24 Hours?

longhorn89 wrote:

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.

See if anything here helps:

If an error occurred while updating or installing macOS - Apple Support

Your internet is weak or there may be density on the servers. If you don't want downloads to go back to the beginning, do this: Turn on Settings, General, Sharing, Caching Contents, so the download resumes where it left off. When you expand this option, you can see how much data accumulates in the cache.