A family of Microsoft word processing software products for creating web, email, and print documents.
Since it worked before and then stopped, something changed. The fix depends on what you see now, so start by sorting out which case you are in. If the Dictate button is missing, first check the account shown under File, then Account. Dictate needs an active Microsoft 365 subscription, so make sure you are signed in with the account that holds it. If the button is there but greyed out, open a new blank document and try Dictate there. If it works in the blank document, the problem is in that one document, not in Word. A document opened from email or the web can open in Protected View. Click Enable Editing if you see that banner. If the button works but no words appear, check the microphone. Go to Settings, then Privacy and security, then Microphone, and make sure Word and desktop apps are allowed to use it. Check that the microphone is not muted and that Dictate is set to the right input device. Click the gear on the Dictate toolbar to check that. Dictate also needs an internet connection, so test it while you are online. One more test that narrows it down. Try Dictate in Word for the web. If it works there, your account and microphone are fine and the problem is in the desktop install. Then update Office from File, then Account, then Update Options, then Update Now. If you can, tell us which of the three cases matches yours and the exact message if one appears. That detail points to the right fix.
This answer was prepared with help from Muse.