It looks like the UTM-generated certificate (for HTTPS filtering) is using SHA-1.
The current version of Chrome will not regard certs with SHA-1 to be fully trustworthy (and subsequently not displaying a padlock).
Future versions (Q1 of 2015) will show a padlock with a red X on it.
Any plans to upgrade the UTM to SHA-2?
This thread was automatically locked due to age.