Dell Wyse 3040 on USB boot says, No images are available on the source USB drive.

I created a bootable USB with correct image on it with the help of USB imaging tool. I tried to boot the Wyse 3040 from this USB and it works but at the final stage the message appears that the No images are available on the source USB drive. I tried couple of time but no success. Even I format the USB drive and new image created but no success.

Anyone can help.

Thanks in advance.