"Mengapa ini tidak diumumkan sekarang?"

Translation: Why isn't this announced now?

[joeldipops]

Not a great English sentence.

I tried with
"Why not announce this now?"
but that might change the meaning too much.

"Why hasn't this been announced now"
Might be better.

[angbagongquezon]

Both of your sentences aren't better than the one above.

[donny309620]

With a different inflection (intonation): "Why this isn't announced now?"

[Hans726]

Why isn't this being announced now

[mundo_e]

Why is this not announced today?--- why not?