The microphone is not working
Dictation needs a browser microphone permission and a secure connection; the button hides when neither is there.
No button at all: the browser does not expose a microphone on this page. Use Chrome, Safari or Firefox, on https.
The button is there but nothing is written: allow the microphone in the browser's site permissions (the lock icon in the address bar), then try again.
It stops after a minute: that is the cap — it transcribes what it has and you press again.
まだお困りですか？
何が起きたかお知らせください。1営業日以内に返信します。