[HELP] after encoding ass into mp4, but there is no subtitle at all

[Selur]

have you tried to encode the ass into the MKV? is the result good?

Yes, that is what I wrote in my last post.

Vapoursynth preview (Filtering->Vaporusynth preview)
you mean this?

Yes.
No clue why the script is empty for you, since you do not care to share a debug output.

Cu Selur