Question Light on lorex N910A6-Z motherboard flashing

[KingofBattle76]

Have a lorex N910A6-Z 4k hd 8 camera nvr with a dahua system board. The has a green light that flashes on and off every two seconds. Why?

 

[rgd1101]

https://d2zri47w41ywm3.cloudfront.net/downloads/security-nvr/N910/N910_MANUAL_EN_R1.pdf