The latest SVG API doesn't work with the examples shipped with the Activiti Modeler.
Firebug's Console shows the error message "ha is null" at signavio-svg.js (line 9), which reads:
This may be due to the models being created with an older Version of Signavio. A workaround might be to export the JSON representations of those models into the latest Signavio version and export them from there. Besides this possibility, this should be seen as a regression in the SVG API as older versions of Signavio/Oryx might still be in use.