I have a base 2017 iMac running Big Sur 11.3, and when I go to Software Update in System Preferences, it says "Your Mac is up to date - macOS Big Sur 11.3." 11.6 should be available. I didn't get notifications for 11.4 or 11.5 either. The only way I can get it to update is to find Big Sur in the App Store and click "Get", but this appears to download the whole installer, and not just the update. What is going on?
iMac 21.5″, macOS 11.3
Is your iMac connected to your router via cable, this will provide a more stable connection to Apples Servers.
Have you tried using the Terminal to ask for software updates.
Open Terminal and at the prompt enter this text
softwareupdate -l
this may take a while so be patient
if you get a list of updates available you can then install them by entering this text
softwareupdate -i -a
or for individual updates
softwareupdate -i 'name of update in single quotes'
Read more here, https://www.howtogeek.com/347920/how-to-download-macos-updates-using-the-terminal/
There are two of them running.
I've done the manual update to 11.6 now. I won't be able to do any more troubleshooting until another update is available, probably Monterey.
Yeah, I had already looked at install.log. I posted a excerpt from it above. Thanks.
As macOS Big Sur is at the moment the current newest OS you do not receive Security Updates separately.
The latest security updates will be included in the incremental version updates.
if you are now running version 11.6 you are up to date with Security Updates.
You may want to look at the install log to see if it gives you any idea why software update was not working.
Open a Finder window and press the Shift Command and period/ full stop keys together this will show the
hidden files on your mac.
The Install log should be in the path below (this is the default path for older macOS's I hope it is the same in Big Sur)
/private/var/log/install.log
the install log could be a very long file so start at the bottom and go up to a time when you know you were asking software update to search for updates and see if it gives any indication of what might be wrong.
Updates not showing in Software Update