Hi,
can you double check a few things?
1) double check it is really installed. go to control panel, installed apps and check if it is really installed.
2) assuming it is installed, can you make sure the plugin is enabled to run? maybe the simplest thing is to reset IE settings, close open and try to connect to devmode. IE should show a message asking to confirm if you want to run the plugin.
3) what antivirus do you have if any?