Try these steps in order:
- Verify that Microsoft Bopomofo is the active keyboard.
- Go to Start > Settings > Time & language > Language & region.
- Next to the Traditional Chinese language, select ... > Language options.
- Under Keyboards, confirm Microsoft Bopomofo is present.
- If it is missing, select Add a keyboard and add Microsoft Bopomofo.
- Remove any unexpected keyboard layouts under that Traditional Chinese language.
- In the same Language options page, under Keyboards, remove any unrelated keyboards.
- Then sign out of Windows and sign in again.
- Open the Bopomofo IME settings and check input assistance.
- Right-click the IME options icon in the taskbar/system tray and select Settings.
- In Bopomofo settings, make sure input assistance options are enabled, especially Prompt associated phrases of the input characters.
- Test candidate selection behavior.
- With Chinese (Traditional, Hong Kong SAR) and Microsoft Bopomofo active, type the Bopomofo symbols for a word.
- Press the Down arrow key to open the conversion candidate window.
- In that window:
- Up/Down moves through candidates
- Enter selects the focused candidate
- Number keys select a candidate directly
- Spacebar moves to the next page
- Tab expands the list
- Esc closes the window
- If the issue happens in apps such as Excel, use the temporary IME compatibility workaround.
- Go to the IME settings for Traditional Chinese Bopomofo.
- Select General.
- Under Compatibility, turn on Use previous version of Microsoft IME.
- This is a temporary workaround, not a long-term recommendation.
If the candidate window still does not appear after reinstalling the keyboard, the most relevant documented fix is to re-add Microsoft Bopomofo, remove unexpected keyboards, and then sign out and back in.