Security Update 2019-006 10.13.6 will not install on my Macbook Air Mid-2012 laptop.

I had the same issue with my late 2009 iMac (first time this occurred with any security update - generated a "An error occurred while updating firmware" message). I rebooted after quitting the Installer, downloaded the Security update a second time and was then successful in restarting. Best wishes with your issue.

unfortunately does not work with Macbook Pro (TB 2016), no error showing, update still showing in Mac App Store. Did try many times safe mode, tried to download update file, tried alsou through Mac App Store. No siccess, the same now with 2019-007 security update.

Let me answer, as I have the same behaviour.

Even in Safe mode, after installation of the Security update and restart, going to the App store –> Updates, the update is shown again, as it was not installed.

Same result when trying to install 1) from App store, 2) downloaded installation package, both in safe and "normal" mode

Yes I did.

I've:

1) downloaded from App store and installed in Normal Mode

2) downloaded from App store and installed in Safe Mode

3) downloaded from Apple support pages and installed in Normal Mode

4) downloaded from Apple support pages and installed in Safe Mode

Still system shows uninstalled security update :-((

Exactly the same result is with Security Update 2019-007 10.13.6

System software information shows "macOS 10.13.6 (17G65)"

Try it in Safe Mode...

Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?

But have you tried downloading it not from the AppStore & installing it inSafe Mode?

https://support.apple.com/kb/DL2023?viewlocale=en_US&locale=en_US

How do you quit the installer?

CMD+q usually.

Trying to recall. It may have been an option in a dialogue box. If not, I may have pressed the escape (ESC) key.

Perfect solution. Thanks.

:)

Safe mode restart takes "forever"; but the result is the same - when I go to About This Mac and check for updates, 10.13.6 still shows with a Restart button; pressing Restart starts the cycle again.

You mean just going to about this Mac crashes it, or the Appstore, or what exactly?

Also see this...

https://davidsimpson.me/2018/11/14/fixing-failed-macox-10.13.6-security-update-2018-002/

Thank you for the tip.

Did those steps, result without change, update still showing as uninstalled.