problem of dual image boot

Hi dialog,
I am doing test about dual image boot with secondary bootloader.
I have sucessful download product_header , ble image file, and bootloader to SPI FLASH with smartsnippets.And the bootloader do run to end correctly(I add some log info to uart), but the ble image file do not work. However, when I download secondary_bootloader.proj to the board with SWD, the ble image file can work now!
I use the command "mkimage.exe suota.bin version.h souta.img" to generate ble image file.
I could not find what is wrong while using smartsnippets, the code of secondary_bootloader.proj is the same in both way.
你能电话l me which step might be wrong when I was doing this?
looking forward to receive from you.
Best regards.