Go through the below steps:

Symptoms typically include:

• No subtitles displayed
• Wrong subtitles displayed
• Hard of hearing subtitles not displayed
• Subtitles on the wrong place on the screen

The subtitle feature is enabled by pressing the SUBTITLE (CC)  button on the TV remote control.
Content for which subtitles are available are as follows:

• TV broadcasts: Subtitles may not be available for some TV broadcasts.
• Apps: Whether a given app supports the subtitle feature depends on the app. Some apps, such as Netflix, enable subtitles by using their own setting menu instead of pressing the SUBTITLE (CC)  button on the TV remote control. In addition, some apps can change the text size and color.
  • Visit the support site of the apps for detailed information, including how to enable features.
  • As of February 2021, the above information is confirmed. The specification of Netflix is subject to change without notice.
  • For YouTube, subtitle feature can be enabled by pressing the SUBTITLE (CC)  button on the TV remote control.

If you encounter issue in retaining the subtitle setting, please refer to I changed the subtitle setting, but the setting is not being retained.