The App Store app doesn’t seem to get any better: for the first time here, it failed to install the Sierra 10.12.6 update once it had been successfully downloaded. That behaviour has apparently become increasingly common with recent Sierra updates. So what should you do when the App Store doesn’t download and install an update properly? How do you work around its bugs?
No progress bar shown
If you click on the button to install an update and the button becomes disabled (greyed out) but no progress bar is shown in that window, locate that app’s icon in the Finder. Chances are that will have a progress indicator to tell you when the update is installed.
Update downloads but fails
If the app downloads the update but then reports any problems installing it, try quitting the App Store app and starting again. You may not be offered that update again, though: sometimes updates seem to get pulled, or the App Store is unable to deliver that update, and you must leave it a while before trying again.
If the App Store app repeatedly fails to install an update, you can try trashing the app and installing it again from the Purchased page. The snag with trying this is that if this too fails, you can lose all access to that app, at least for a while.
macOS update downloads but does not install
This is happening with significant frequency now: the progress bar completes, you are notified that your Mac will restart, and nothing further happens. The update may still be offered to you in Updates, but clicking on the button does nothing, not even start the download again.
The best thing to do next is save any open documents, quit all open apps, including the App Store, and then use the Finder’s command to restart your Mac. It should then recognise that it has a macOS update ready and awaiting installation, and you will be invited to install that update before restarting. This should then engage the update mechanism properly, and that update should proceed normally.
macOS update installs, but it all goes wrong from there
I deal with this in a separate article. The single most valuable solution is to download the standalone Combo update, and install that, if you can.
You keep getting offered the same update
This happens every so often. It is impossible to know whether these multiple updates are really needed, or whether the App Store is just having a brainfart. The simplest solution is just to play along with it, and keep downloading what may be the same update. Sometimes the first update is small, and a second time it is significantly larger: that suggests that there was a problem with the first update, which is rectified in the second.
Treat the App Store like you would a reasonable politician: don’t believe everything it tells you, and don’t expect it to tell you everything accurately. Then it shouldn’t disappoint or infuriate. Too often.