This is known as a boot loop. Try removing the CMOS battery for 30 seconds to reset the BIOS settings, or contact technical support for a TFTP recovery tool. Where to Find the Download
Use a Surge Protector or UPS. If the power cuts during the flash process, the DVR may become unusable. dvr116gf1 firmware
There are generally two ways to update this model: via USB or via the Network/Browser interface. Option 1: Update via USB (Recommended) This is known as a boot loop