GNOME Shell 3.16.4
MMOD-Panel v1.1.1-7
When setting the Position to "Bottom" for MMOD-Panel, then when clicking on the main networking/battery/audio/brightness applet, and clicking on "VPN", it does not expand. When the MMOD-Panel position is set to "Top", "VPN" expands perfectly fine.
EDIT>> It seems this only happens when there are a large number of VPN items to show. I had around 25 or so (a script provided by PrivateInternetAccess added a large number of VPNs). Once I dwindled the list, it now works as expected for both the "Top" and "Bottom" locations of the panel. This may be an issue with the gnome panel and not with MMOD. If so, please feel free to close this.