I assume that neither the front panel control buttons nor the remote control commands work. If this is the case, it could be that the TV is stuck in a video input mode where there is no signal connected.
Have you checked all around the TV (the rear, sides and bottom) for a reset switch? This could be either a surface-mounted rocker or push-button switch, or it could be a recessed pin-hole type switch (one that is accessed by using a small object such as an unfolded paper clip that is inserted through a small pin-hole opening to push/depress the switch). Not all TVs have hardware reset switches. If your TV does not, you can try a 'soft' reset, which works sometimes for some brands of TVs. It won't hurt anything to try.
1. Unplug the TV from electrical power. Leave it unplugged for about ten minutes.
2. After that time, and while stilled unplugged, press and hold the TV's main Power On/Off button for about 5 to 10 seconds. Release it.
3. Press and hold each of the remaining buttons on the TV, one at a time, for about five seconds, and then release. DO NOT use the buttons on the remote control - only use the buttons on the TV itself.
4. Press and hold all the buttons on the TV simultaneously (together) for about five seconds, and then release.
5. Plug the TV back in. Power it up normally.
6. The TV should start automatically scanning for active channels from your input signal source. Make sure you have a good signal (antenna or cable or satellite).
If the TV still does not display anything, try the menu button on the TV and see if you can access the menu. If not, try using the remote control's menu button.
If the TV is still locked and will not respond to any commands from the front panel control buttons or the remote control unit, it is apparently locked in a failure or diagnostic mode, and would probably have to be diagnosed and repaired by a reputable TV repair facility. Good luck.