Message Text
** ERROR 305375 ** One or more tetrahedral elements with the property type "Legacy hot runner for overmolding second component" have been found in the mesh. These elements are no longer supported. Open the study file in Synergy to convert the elements to the correct type, which is "Hot runner (3D)" with the Component set to second shot on the Overmolding Component tab. Then re-run the analysis. If this is unsuccessful, contact Autodesk support.
Explanation
In past releases, it has been possible to set up for an overmolding analysis using an element type Hot runner for overmolding second component (3D). We announced, with the 2015 release, this workflow and these element types would be obsoleted with the 2016 release. Elements of property type Legacy hot runner for overmolding second component (3D): obsolete are now no longer supported. The model you are working with has elements of this type, which need to be changed. As long as these unsupported element types are present in the model, the analysis will not run.
Resolution
Identify all elements of property type Legacy hot runner for overmolding second component (3D): obsolete, then click 
() and select an appropriate alternative from the Change Property Type to dialog box. Do not select a Legacy overmolding option, since they are now obsolete.
Select the elements that have been assigned a new property type and click 
(). Select the Overmolding Component tab, and identify these elements as either the 1st shot or the2nd shot.