Amazon how to use wired headset with Luna controller/fire tv combo

1. Restart the device.
2. Make sure the device and app are up to date.

Try cleaning Luna app:

1. Go to Settings on your Fire TV.
2. Select Applications.
3. In Manage Installed Applications, select the app you are having trouble with.
4. Select Clear Cache, and then Clear Data.

Try to unpair your Luna controller and then pair it back again, you can get guidance in this link.