Panasonic 55DX600U Turns on then turns off after 1 second.

@jenkinsb01 could be a power board issue as well as the tuner board etc. . we would need to see your boards. Post some good pictures of the boards with your question Bilder zu einer vorhandenen Frage hinzufügen

You will need a multimeter that you can use to measure some voltages etc. to determine which board may have failed.

Is there a way to do a factory reset without turning on the tv? No, there is not. It would be reset once you pulled the power cable and disconnected all inputs. Then hold the power button for a minute or so. After that plug it back in. You can also start by downloading the service manual from here and go through the no power failure to see if that will lead you to the right board.