Toshiba 55L621U Black Screen After Splash Pops Up & Leaves

This was the problem: you turn the TV on and the splash screen (Toshiba Chromecast Logo) comes on and then goes black. The LED on the front right stays red.

I replaced the main board to no success.

I tried to install the newest firmware but it was unsuccessful.  It's note worthy to say the attempt to reload the firmware confirmed the LEDs are not a problem.

I don't know what else to do.

Firmware update failure attached to the end of this video.