Maybe the usb power got cut. Which means it doesn’t allow booting from usb.
Original box didn’t allow booting CoreELEC: Xiaomi Mi BOX - CE and DRM
But I think I saw somewhere how to boot from this device but can’t find the source.
Or this was mibox3? https://www.reddit.com/r/MiBox/comments/uolzc7/if_you_have_a_mibox33c_mdz16aa_you_can_now_flash/