Check out Blackberry Virtual Expert in the Play store. Run through its various tests.
But try
From BB blog:
How to reset PRIV by BlackBerry | Inside BlackBerry Help Blog
Three restart/reboot methods
The first method, which should be used 99.9% of the time when you want to reboot your device, is using the Reboot option that appears after pressing the Power key.
Press and hold the Power key for 3 seconds
Select Reboot from the menu that is presented
The second reset method should be used if pressing the Power key does not produce the menu with Power Off and Restart. For example, if an app or game you are using won’t close, use this option to restart your device.
Press and hold the Power key for 12 seconds
Third method: Should your device fail to respond, the final reset method is to press and hold the Power key for 32 seconds which is equivalent to removing the battery. This should result in your device booting up successfully.
If it fails to start, however, verify you are not pressing any other keys such as Volume Up, Mute, or Volume Down while performing any of the reset methods listed above. If you use a case for your device you may want to remove it as it might be pressing a button inadvertently.