Automatic Update doesn't download

I have Automatic Updates set to "Notify me but don't automatically download
or install them".

I get the notification of a new update and click to see what the update is.
Then I ensuring that an update is selected, I click on download. The window
closes and the icon in the system tray disappears, nothing else happens.

Any suggestions please?

It may be significant that I have amended the default services several
months ago to stop unwanted services - according to a list of recommended
services I found.

Peter