I have a 2029 iMac that has not been updated in a while, currently using MacOS 10.15.7. Catalina I was overseas so did not update the software for a while. I am trying to update the system, 620 GB storage is available.
More information will be needed, but not until 2029.
To identify your model iMac please read Identify your iMac model - Apple Support.
Assuming you meant a 2019 iMac you can get it from the App Store.
https://apps.apple.com/us/app/macos-sonoma/id6450717509?mt=12
Try upgrading while in Safe Mode.
+1 on restarting in Safe Mode and trying to upgrade.
if by chance you have any third party AV, cleaning VPN or other similars apps those could very well be a major issue(s)
I went too far in future, apologies, yes I meant 2019, and have tried to update from App Store, it keeps on "Finding update" but nothing happened even after many hours. I have connected internet via ethernet cable just to ensure that the download speed gets better. No luck so far.
Unable to update iMac from MacOS 10.15.7 to MacOS Sonoma
