Try holding down the standby button for at least 15 seconds.
When the HS2 initiates it checks the HDD is working and then checks a valid disk is in the tray. If either is broken (i.e. the HDD is faulty or, more likely, a defective disk is in the tray) it will not boot up. You can get around the latter issue by holding down standby for 15 seconds or more and pressing eject. If it's not a disk it could be the HDD. Like any PC the period when a HDD is likely to fail is when it's a new drive.