If the Cirrus Insight icon used to show up but is no longer appearing in the toolbar, the most common reason is that Outlook disabled the plugin. To re-enable the plugin, use the following steps.
If the plugin was installed but has never been visible in the tool bar, try re-installing but choose the install option for JUST ME.
This is typically only needed for Outlook 2010 and prior versions. When reinstalling, three screens will appear. The second screen shows the option “Just Me” selected in the lower left part of the screen. Choose this and then continue the install. Restart Outlook when complete