A Fire TV is sold as a television accessory, so it ships configured to power down when nobody is using it. That is the opposite of what a signage screen needs.
The Screenly app starts itself when the device boots, so a screen recovers from a power cut on its own with nobody visiting the site. Fire OS is built on Android, so the same two device settings have to permit it first, and both are off on many devices.
Turn off sleep and the screensaver
In the device settings, turn off the screensaver and any sleep timer before leaving a screen to run on its own. Both are on by default.
Allow display over other apps
Screenly needs permission to put itself in front of whatever the device shows at startup. Without it the app starts but sits behind the launcher.
Open the device settings.
Find the app permissions for Screenly.
Enable the permission usually called Display over other apps.
Some devices name it Appear on top, Draw over other apps, or Floating window.
Allow the app to start on boot
Android tells apps when the device has finished booting, and Screenly listens for that. Some devices ship with a security or power-management app that blocks that boot message from reaching apps, which is usually what prevents an otherwise correct setup from coming back on its own.
- Open the device settings and look for an autostart, startup manager, or permission manager.
- Find Screenly in the list.
- Allow it to start on boot.
The names and locations of both settings vary between Fire OS versions. If you cannot find them, search the device settings for “autostart” and for “over other apps”.
Check it worked
Pull the power, wait, and plug it back in. The screen should return to your content without anyone picking up a remote.
Test this before a screen is mounted somewhere awkward. A screen that needs a person to press a button after every power cut is the most expensive kind to run.