Please disconnect the set from AC power for 2 minutes, then upon plugging back in, press and hold the power button for 8 seconds to try and force a reset.
If the TV still does not power up, then there is a short inside the set stopping it from fully powering up.
Most probably there is a failure on the power supply board inside the TV. Commonly the capacitors on this board will receive a surge and then fail.
They can sometimes be visually verified by removing the rear of the set and inspecting them for bulges or leaking fluid at the top or the base of the caps. This is the most common mode of failure for these sets.
The capacitors are located on the power board inside the set, where the AC cord plugs into and can be replaced by a technician for no more than $200 (parts and labor). There is no sequence of buttons or reset you can perform to get the set working again.
Do you have any experience testing live voltages, or soldering on electronic equipment? If not, then I would suggest using the link below to locate a technician in your area:
If you need further assistance, let me know.