You have a PC with Windows 8 or Windows RT installed on it.
Through the Language applet in Control Panel, you add Chinese (Traditional, Taiwan) as an additional language to use in Windows.
In this scenario, no Windows display language is available for download. However, if you choose other regions that use Traditional Chinese such as Hong Kong SAR or Macao SAR, Windows display languages are available for download.
This behavior is by design. While the Chinese (Traditional, Taiwan) language pack can be found on PCs available in Taiwan, Microsoft is unable to release the language pack outside of Taiwan. For this reason, this language pack is not available on Windows Update and cannot be downloaded using the Language applet in Control Panel.
To resolve this issue, use the Chinese (Traditional, Hong Kong SAR) language pack instead. This language pack is intended for worldwide users of Traditional Chinese even though the region is shown as Hong Kong.
LP language pack