Hi @George Arian,
Here’s the [https://elektrotanya.com/panasonic_th-p50xt50a-d-g-k-m-p-s-v_chassis_gpf15d-a.pdf/download.html|service manual] for the TV. Be patient as it takes a little while to go from ''processing'' to ''download'', after you have passed the security test and clicked on Go to Download, below the document preview box.
Go to Sect.7.3 on p.20 to view the ''No Power'' trouble shooting flowchart. This may be the best place to start to find out what is wrong with the TV.