The latest system update, accd to my phone issued August 27th (in England), downloafs, installs (including restarting the phone), continuously. Done it 6 or 7 times since yesterday, but it keeps telling me the latest version is available.
Do you know if your device was updated to the latest version prior to you receiving this notification? The way updates work is that you can only install one at the time, so if you have more than one to install, you will get a new notification after it has been installed and the device has been rebooted.
The easiest way to check this is if you go to Settings > System > About phone > Build number. Do the update and check the build number again. Did it change?
