A friend of mine has 27inch iMac and its fusion drive failed.
She had the drive replaced with an SSD by a well established repair shop in London. Everything went swimmingly and afterwards it asked for the TM for do a restore.
One possibility: if the computer completed the “new computer setup” process after the new SSD was installed and Migration Assistant was launched from the Finder, there may be a conflict between the macOS User ID created during setup and the User ID on the Time Machine backup.
(I haven’t had to deal with this issue for a long time but as I remember, macOS assigns User ID 501 to the macOS user account created when “new computer setup” happens. If the Time Machine backup also belongs to a User ID 501—likely if the TM backup comes from another Mac or HDD/SSD—Migration Assistant won’t allow the newer macOS user account to be replaced by the older macOS user account)
Possible solution: Reset the Mac to factory settings. Follow the “new computer setup” process, using the TM backup when prompted.
(if you’re indeed looking for a holiday resort for a Time Machine, I suggest Goa)
;-)
Fish commented: “I was able to reset the user password, but oddly, TM does not appear to have restored anything from the user account.
Any comments please.”
Yes, but they won’t help immediately – only in the future. Stop using time machine. Start using either CarbonCopyCloner or SuperDuper instead.
If your friend had used either one for backups, she’d be up-and-running already.
Disclaimer – I have no financial interest in either of the above two apps.
They just … work … that’s all.
(…when tm doesn’t, as your friend found out).
I agree with what @Halfsmoke noted. Since this Mac doesn’t have a T2 chip (you said it had a Fusion drive, and those Macs didn’t have the T2 chip).you can’t use the “Erase all content and settings” route to get a clean macOS installation. You’ll probably need to re-format the startup disk with APFS using the information in Use Disk Utility to erase an Intel-based Mac - Apple Support. After you’ve reformatted the boot drive’s Macintosh HD volume, reinstall macOS from Recovery using the information in How to reinstall macOS - Apple Support.
I personally don’t reinstall applications from a Time Machine backup. I prefer to install them manually on a freshly installed macOS so that I don’t carry over cruft that builds up over time. But I leave that decision to you…