The hard drive can cause the NVR to stay on the "Loading..." screen. The listing you provided shows that this did not come with a hard drive. If you installed your own drive, be sure that it meets Zmodo's recommendations. See this KB article:What Kind of Hard Drive Will Work in a Zmodo DVR?.
If the drive meets those recommendations, try powering off the NVR, disconnecting the hard drive, and powering it back up. If the NVR powers up properly without the hard drive connected, then you know the issue is the hard drive.
If the issues persists without a hard drive, and your NVR is still under warranty, you can submit a warranty repair request online at www.zmodo.com/rma/.