English Translation
You must not go out today.
The audio does not match the katakana.
Incorrect Clozemaster transcription in Hiragana: 君【きみ】は今日【きょう】外【がい】に出【で】てはならない。
→ Correct: 君【きみ】は今日【きょう】外【そと】に出【で】てはならない。
Clozemaster TTS pronounces like きみは / きょうそとに / でては / ならない, but this word split regards 今日外 as a single compound, and that makes the pronunciation unnatural although understandable. Try Google Translate’s TTS instead by typing 今日、外に出る with a 読点 (、) inserted. You need a short pose between 今日 and 外.
Also note that you need to put a high pitch accent on the first syllable そ of 外. It is weird but Google puts an accent on the second syllable と of 外 if you type 君は今日、外に出てはならない instead of 今日、外に出る.