DIAGNOSIS The TV is stuck in a boot loop, usually caused by a failed firmware update or corrupted internal memory.
FIX Perform a power cycle with a specific sequence. Unplug the TV from the wall. Hold down the physical power button on the TV (not the remote) for 30 seconds while it's unplugged. Release, plug the TV back in, and try turning it on with the remote.
IF THAT DIDN'T WORK Try a factory reset using the button combo. With the TV plugged in but off, press and hold the Input and Volume Down buttons on the TV's back panel. While holding, press the Power button on the TV. Keep holding the first two buttons until the TV powers on and displays the reset menu, then release.
HEADS UP A factory reset will erase all your settings and logged-in apps, so you'll have to set up SmartCast and Wi-Fi again from scratch.