BeagleBone Black's EMMC does not show up when booting from MicroSD card

We have been using BeagleBone Black manufactured by GUI for years and program it with MicroSD card. This time we do the same thing on the Seeed’s BeagleBone Black purchased from

But EMMC does not show up when booting from MicroSD card? Could someone help? Is there a jumper that can make EMMC show up?

Thanks,
Timothy