1.Go to Fire TV Settings
2.Select Audio Settings
3.Turn off Dolby settings
4.Change the audio output
from Dolby Digital to PCM settings
This should help to resolve any audio issues
caused by compatibility problems between the device and your audio system. If
this doesn't resolve the issue, you can try other troubleshooting steps such as
restarting the device, checking your audio cables, or resetting your audio
system.