If the app cannot find your Fire TV or the buttons have no effect, check the following.
- ADB debugging is enabled on the Fire TV (see « Connect the app »).
- The phone and the Fire TV are on the same Wi-Fi network (watch out for « guest » networks or split 2.4 / 5 GHz bands).
- The Fire TV is turned on.
- You confirmed the « Allow USB debugging » popup on the TV. If you declined it: Developer options → Revoke USB debugging authorizations, then reconnect.
- Enter the Fire TV's IP address manually if the scan fails.
- As a last resort, restart the Fire TV and your internet router.