Can't place System Panels in arced Curtain Walls created prior to 3.0, nor in straight Curtain Walls created prior to version 2.0. 
   Namespace:   Autodesk.Revit.DB  
  Assembly:   RevitAPI  (in RevitAPI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
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