Link :
https://vip.asus.com/forum/view.aspx?SLanguage=en-us&id=20170221184228273 . I've exactly same problem with my motherboard.
QUOTE :When i turn on the PC.... it boots perfectly the LED turns on and off one after another and then everything remains off when i am in Windows.
Now when the PC goes to sleep ( not shut down) and i wake it up... the Boot LEDs does the same process really quickly but hang on the BOOT_DEV LED, eventhough i am in windows.... Am i missing something ?