2017 iMac can't start up, freeze at apple icon and half of the progress bar.
Things I tried:
(1) First Aid, all scanned and no problem found.
(2)I tried Recovery to reinstalled Monterey and got the following message: Com.apple.Buildinfo.preflight.error error21. I changed to differnt Wifi, same error message; Connected directly to ethernet, still got same error message.
(3) I tried to add volumne and install Montery, no problem, but I still can't access to the Macintosh HD.
(4) I tried to backup, create image of the Macintosh HD, but it was greyed out.
Now really don't know what else I can do. I did search online for solution, I noticed someone else asked same question, but I didn't see any solution.
Please help! I have lot of files on the hard drive, can't lose them. No budget for a new iMac at this point.
Thanks in advance!
iMac 27″ 5K