Keyur Kanade
Ansys Employee

One of the main reasons in failure is geometry errors. Please check geometry in SpaceClaim. Select geometry in structure tree --> Use right click --> Select Check Geometry. The geometry should be error free to proceed. If geometry has any errors, please modify/recreate geometry at those places.

Another reason is having some tangential contacts at some circular surfaces. Please make sure that bodies are intersecting instead of just touching each other. 
Sometimes bodies are in contact only at some edges. At this point volume extraction may fail. In this case as well please make sure that bodies are intersecting each other. 
You mentioned you have geometry from third party software. Please make sure that you do not have it in faceted format. Please convert it in geometry format.