2012 MacBook pro white screen. Notting works!

Hi all, my 2012 MacBook Pro has stopped working for over 12 months now due to a white screen appearing (no logo etc) In the past I have purchased a new HD cable which seemed to have solved the issue, however after replacing them multiple times, including buying a new HDD, it still only shows a white screen. I have tried all the key combination/ restart options and only the “option/command/p/r“ combo gives a respond by restarting...back to the white screen. Connected old HDD externally to old iMac and repair etc was all greyed out. I can’t even reinstall OS X. Can someone please tell me if there are any options left or is it time to trough it out?

Thanks in advance! Jeff