Can't find /tmp/rootfs/boot/uEnv.txt when Extracting eMMC contents

I am extracting eMMC contents to sdCard on my BBB, when running the sell:
sudo /opt/scripts/tools/eMMC/beaglebone-black-make-microSD-flasher-from-eMMC.sh

I got a error:
sed: can’t read /tmp/rootfs/boot/uEnv.txt: No such file or directory

Any helps?
Thanks!