firefox could not input Japanese

Hi,

I used ubuntu-20.04.4 , ibus-mozc and firefox 99.0.
In web site, I input Japanese and English alternately sometimes.

Recentory, I change Japanese to English using hankaku/zenkaku key.
and I input English sentence.
then I return Japanese to push hankaku/zenkaku key.
but I could not input Japanesei.
in top menu, status changed to Japanese.

in this situation, other applicaiton(test editor) could input Japanese.
So, I input Japanese text in text editor, then copy & paste web page in firefox.

today, I found it, I click in top menu Japanese (Mozc), then I can input japanese.