My panasonicTC-P50UT50 50in Plasma tv power light is flashing 8 times and won't turn on. What does this mean?

Could be the main board died, PSU is going, bad caps somewhere along the way, any one of the chips on board.

Other than unplugging it for a while and then plugging it back in, I'm not sure what you can do. You'd have to take it to a TV repair man, but the costs of such TV repairs are so expensive now for parts, that usually a new TV is cheaper. Especially with Black Friday coming.