Illustrator SDK :: AIDocument - GetDocument Fails With AIErr DOC?

I am trying in Illustrator 64 on Windows through a plugin to open  document and get the documents setup.My code is as follows.
 
I first acquire the required Suites ( AIDocument, AIDocumentList, AIFilePath etc ) and all the Suites are acquired with NO Errors and have valid pointers
 
AIErr err = kNoErr;
//Get the page information
  AIDocumentHandle theDocument;
ai::UnicodeString uniPath( "C:\test.ai");
ai::FilePath fpath(uniPath) ;
err = sAIDocumentList->Open( fpath, kAIUnknownColorModel,kDialogOff,
false, &theDocument );  
[code]....

I have also tried using AIDocument->GetDocument and AIDocumentList->Activate both after opening the document and they also return DOC?, though the theDocument Handle returned by open document appears to be valid.