Check the Output on the power supply going to the DVR. The output for this DVR should be 12V and at least 3A. Then try plugging that power supply directly into the wall instead of a power strip, power surge, or battery backup.
If none of these things work, you might test the hard drive with a computer, (just to make sure), and then replace the DVR’s power supply. If the DVR’s power supply is defective and you are under warranty, you can submit an RMA to request a replacement.