How can I get my HTC M8 working again?

[AC Question]

htc m8 switched off forever without any reason.

Ond day my htc m8 didn't wake up screen when I double tapped it. Then I JUST RESTARTED IT. From that point onwards it doesn't turn on. When connected to pc or power red led blinks twice in regular intervals. Tried everything on internet to restart pressing buttons and everything. It doesn't turn on. NO SCREEN AT ALL. ALL BLACK. Now I'm hopeless and trying to find a new motherboard for this. Any suggestions please? I used this for more than one year...