The solution to Fire TV Cube has no audio.
1. Restart your Fire TV Cube. Unplug the power.
2. Wait for 3 seconds, then plug the power back.
3. Check if your Fire TV Cube has the latest system.
Go to
Settings >
My Fire TV > About > Check for System Update.
4. Check the TV speaker.
Select
Settings and select
Display & Sound. If it has been turned off, turn it on.