The built-in microphone doesn't seem to work and the TV fails to react when I say OK Google.

Note for X77L series: To use this feature, you may need to press the Google Assistant (MIC) button on the remote control four times until a pop-up message appears. If a pop-up message appears, select Yes, I'm in.

1. Check the Built-in MIC Switch status on the TV body. If it is set to OFF, set it to ON. If it is set to ON, set it to OFF, and then back to ON again.
   Note: The location of the Built-in MIC Switch button differs depending on the model. The image below is an example.
   
2. Make sure the Hands-free mic is set to On.
   1. Open the Settings screen. How to access the Settings
      • If the remote control has a Quick Settings ( or ) button, press the Quick Settings button and select Settings.
      • If the remote control does not have a Quick Settings ( or ) button, press the HOME button and select Settings.
   2. Select Privacy.
   3. Select Google Assistant.
   4. Enable Voice control.
   5. Enable Hands-free mic.
      
   6. Select Done.
      Note: For some models, the Hands-free Mic setting was added by an update. If the Hands-free Mic does not appear under Google Assistant on your TV, make sure the Auto-update apps at any time setting is enabled in your Google Play store profile.
3. If the issue still happens, follow these steps to clear the Google Assistant app data.
   1. Open the Settings screen. How to access the Settings
      • If the remote control has a Quick Settings ( or ) button, press the Quick Settings button and select Settings.
      • If the remote control does not have a Quick Settings ( or ) button, press the HOME button and select Settings.
   2. Select Apps.
   3. Select See all apps.
   4. Scroll down to the bottom of the list and select Show system apps.
   5. Select Google.
   6. Select Clear data.
   7. Press the MIC button on the remote control and, at the Control your TV with "Hey (Ok), Google" screen, select Yes, I’m in.

1. Press the HOME button on the remote control.
2. Select Settings.
3. The next steps will depend on your TV menu options:
   • Select Device Preferences → Google Assistant. (Android™ 9 or later)
   • Select Google. (Android 8.0)
4. Turn off the OK Google detection, then turn it back on.