Missing icons after change to Adwaita

I have installed Ubuntu 16.04 on my desktop computer. After changing the theme to Adwaita, I have some icons missing - e.g. gEdit icon, icons in AisleRiot.

The strange thing is I have exactly the same set-up on my laptop computer, and the icons show. And I also had the same set-up on the desktop machine itself for a few weeks, until the hard drive went on the blink (hence the new install now on a new drive). The contents of the folder /usr/share/icons/Adwaita/ appears to be the same on both machines.

How can I get these missing icons to appear?

David