I have the same issue and have confirmed in the user activity log that the activity was captured. I'm just testing to figure out how I can use the link ID to track downloads, so the link HTML is:
<a href="http://learn.company.com/GD---2016-ROI-Study_LP-Infographic.html?utm_source=email" target="_blank" id="download">
I know the smart list is set up correctly, so I'm guessing my issue is in the code. What am I missing?