Troubleshoot Japanese on Mac when you can’t enter characters
If you have another keyboard, try using it. If the characters displayed correspond to the characters you press on the second keyboard, the original keyboard may not be working correctly.
On your Mac, do any of the following:
Make sure a Japanese input source is selected in the Input menu in the menu bar.
In the Keyboard Viewer, make sure the characters displayed correspond to the characters you press on the keyboard.
If you think that converting every character may be preventing some characters from displaying, turn off Live Conversion. Instead, use traditional conversion.