Hi TJohnson,
As my colleague Arnost Lobel said, Transaction might not be needed, I tested your code and removing it makes the exporter work, can you please try it and let us know if you are good to go. Arnost the dialog is the one launched by Revit when the Document.Export call uses for the NWC file to be created.
Here is how your code looks now.
Snippet
UIApplication uiapp = commandData.Application;
UIDocument uidoc = uiapp.ActiveUIDocument;
Application app = uiapp.Application;
Document doc = uidoc.Document;
//create NWExportOptions
NavisworksExportOptions nweOptions = new NavisworksExportOptions();
nweOptions.ExportScope = NavisworksExportScope.Model;
nweOptions.ViewId = uidoc.ActiveView.Id;
doc.Export(@"D:\Shared", @"test.nwc", nweOptions);
return Result.Succeeded;