Hi i have just purchased an uno 4k and am trying to flash it. the problem i have is no matter what software i use the led is just blinking slowly and will not flash quickly to confirm the flash has completed however when install the original firmware from vu it flashes and the indicator changes state. i have used three different usb sticks all formatted to fat 32 1gb,4gb,32gb. everytime i reset it still running the orignal vu firmware. help would be appreciated. its driving me mad