I have tested your TTS voice file with tts_nua_ve1 engine and it works (using version 9.19.5.578126) see pictures below of viewing them in the list and selecting the language.
I have attached my sys.txt that I am using this sys.txt works on both TTS engines.
I have also tested the dutch Nuance TTS voice with version 9.19.2.543580 and it works as well see pictures below. I downloaded this engine from [Only registered and activated users can see links. ].
Hope this helps.
Bookmarks