I am having this issue on two computers as well. "Update" doeas nothing, no
new web page, no pop-up. All my blockers are disabled. "Update on scan" is
checked but defender just starts to scan.
That doesn't work either. There better be an update on the program before
all the people who are having this problem are cured. I'm unable to update
either the engine or the definitions..
1) Uninstall Windows Defender.
2) Install original Windows defender V1.0.0.0.
3) Run windows Update via Internet Explorer and install update for Windows
Defender (new version V1.14.1353.2)