Open Settings on your Fire TV
Select My Fire TV or Device & Software
Select Reset to Factory Defaults
Confirm the reset
Wait for the Fire TV to restart and reset
If the remote is not working, press and hold Back and Right on the directional ring for 10 seconds
Select Reset when prompted
If needed, unplug the Fire TV for 60 seconds and plug it back in
Use the remote reset method again if the device does not respond