Hello @淑纓 楊
I just got confirmation that Non-Neutral voice training has been deprecated.
To answer your question about why you can train non-neutral voice model for some languages but not for Japanese: We allow current users to re-train non-neural voices for their existing projects, but they are not allowed to train new voices
For user use non-neutral, we have a short guidance to help you mitigate to neutral training:
Sorry for the inconvenience.