Page.UnlockAllShapes Does Not Work

I attempted to use this method, UnlockAllShapes, on the master page in a document in CorelDraw 2017 and it did not work. I did this using C#.  My code specifically was


For whatever reason this code does not seem to work. The next thing I attempted was a workaround using CQL.  Specifically:

ShapeRange lockedShapes = corelDrawDocument.MasterPage.Shapes.FindShapes("@com.locked = true");
ShapeRange lockedShapes = Page.Shapes.FindShapes("@com.locked = true");

Neither of these function calls returned any shapes even though I know they should work. Does anyone know why this could would not function in CorelDraw 2017?