While start up my phone shows a black screen written unable to find a boot able key

[WPCentral Question]

I have lumia 520. I have tried software recovery tool as well.

 

[mariusmuntean]

Take it to service.

 

[RumoredNow]

I have lumia 520. I have tried software recovery tool as well.

Power off the phone. Try the Recovery Tool again and make sure to use the My phone won't boot or respond option.

​Otherwise, yeah, you need qualified repair.