Babubamboo, If you access the BIOS (F2 at startup) and then go to SYSTEM SECURITY, then "AC Power Recovery"  From there you can set how the system responds from a loss of power event.  Let me know how it goes.
After power failure, the Dell PE R720 can't boot up automatically. Have to press power button manually to power on the server. Can Dell PE R720 auto power up automatically??? Thank you.
Can Dell PowerEdge R720 auto power up??