security update 10.14.6 cannot be downloaded on macos mojave macbook air 2015?

I have a 2012 MacBook Pro (Mojave 10.14.3 )that has a similar problem. It would download the 10.14.6 dmg file but would not allow me to install it:

Got an error message when I tried "This Mac can only install macOS on APFS-formatted drives". If this is what is happening to you the answer I found out is my current hard drive is formatted HFS+ Journalized, so even though Apple says both of our Macs are compatible they don't say your drive (hard or SSD) has to be APFS (Apple File System) Apple has taken a hard stand and unless you have the APFS file drive you are toast I guess.

So here is how you Check what your file drive format is:

Go to upper left hand corner of your screen click on the apple Icon

On the drop down Menu click on "About this Mac" It will bring up a screen with a picture of your current OS below is a rounded box titled "System Report" click on it

Under the HARDWARE section click on "SATA/SATA Express" look for "Content" if it says Apple APFS you should not have any problems, If it say HFS+ you are going to have to reformat your hard drive.

Sorry if this sounds like another language - just trying to share my learning experience, all I wanted to do was upgrade not become an Apple guru

John

There is some issue with the server at this point in time—try again at a later date.

Try this link: https://support.apple.com/kb/DL2031?viewlocale=en_US&locale=en_US