If Philo playback has working audio but shows only a black screen for video, the first thing to check for is a pending Fire TV device update:
Click the Home button on your Fire TV remote.
Click Device & Software.
Click Install System Update.
Finish off by restarting the device: go back to the Device & Software screen and click Restart.
If a system update does not resolve the issue, get in touch and we can investigate further.