Never had this Issue on all of my Asus mobos with the same usb stick.
But this time the Bios Flashback Button Update (which i always use) did not work for me.
Tried this for months, reset Bios before updating and so on..
now i tried this all again..
Someone else have this problem too?
Now i use the bios built option to flash the bios,
which works.
But even now i cant update via Bios USB Flashback button..