Why is mobile not switching on?

[WPCentral Question]

My Nokia Lumia 520 is ot switching on.When i switch on it is showing...ERROR:Unable to find a bootable option.Press any key to shut down.What should i do?

 

[palmujukka]

What's your OS version? Did you do anything special (eg installing an update) before you switched your phone off?

Also have you tried to do a soft reset (vol up + power)?

 

[MDK22]

Dunno if soft reset works on Lumia 520 (removable battery) perhaps a battery pull...
If not, hard reset ... Bing or Google it, it can be accomplished with a key combo (on a dead screen)
FINALLY, you may have to restore using NSU !