J6EVM5777: J6EVM5777 didn't enter the uboot process with the SD card ,which has MLO and u-boot.img, how can I solve it?

Part Number:J6EVM5777

Hi,all.

The board J6EVM5777 suddenly can enter the uboot process with the emmc,so I insert the SD card to it and want to boot it from SDcard.

But both of them doesn't work.

How can I solve it?

Thanks you.