Thanks for trying to help...
Trying to install the update I just get:
Updates could not ber applied"
Please contact your Administrator if you wish to apply updates on your machine.
Updates have been supressed by the administrator"
Tried to delete the updateprefs file also - but it did not help.
I had a similar error message on Mac so I right-clicked (control-click) on the red Install icon inside the download folder choosing:
Show Package Contents >> Contents >> MacOS
You should see a black install icon.
I double-clicked on that black icon and agreed to open an application downloaded from the net, and the installation started and completed OK. This method uses Terminal.
Tried the trick but just got the same sign as described before "Updates have been..."
In the text editor following shows:
Macbook:~ User$ /Volumes/Lightroom-6.12.0-Update/AdobePatchInstaller.app/Contents/MacOS/AdobePatchInstall er ; exit;
...copying shared history...
...saving history...truncating history files...
I also tried to make the UpdateAdminprefs.dat file allowing updates - but this didn't change anything.
Ended up finding the original UpdateAdminPrefs file was present when I looked after it a bit more thorough .... so after renaming the file it all worked.