If you are using Outlook as the thick client (desktop app, not Outlook.com), you may encounter an issue where your Outlook email settings will disable Sparklet. It most likely looks like this:
There are two possible solutions to fixing this issue.
1) In Outlook, go to File, Options, Add-Ins and click on the "Go" button.
A pop-up like the below will appear.
We have discovered that if there are more than THREE (3) add-ins checked, Sparklet may not appear. We recommend that you un-check them one at a time and see if Sparklet is now present or not. If present, it will look like this. Consider restarting Outlook if it does not appear.
2) The other solution may be:
In Outlook, go to File, Options, Trust Center, Email Security. Then click on Trust Center Settings.
Click on Email Security. If there are ANY checks in the boxes, Sparklet will not run. Encrypting an email causes a macro to run which conflicts with the Sparklet extension.
Your Email Security Trust Center should look like this:
If all of these are unchecked, Sparklet will now be active and you will now see the icon, which will look like this: