I am testing secure DFU with hex files under D:\nRF5_SDK_16\examples\dfu\secure_dfu_test_images\ble\nrf52832 folder. After programming softdevice, bootloader, and application hex files through J-Link Commander script, Received an error: 0x00000003 occurred.
0> <info> app: Inside main
0> <debug> app: In nrf_bootloader_init
0> <debug> nrf_dfu_settings: Calling nrf_dfu_settings_init()...
0> <debug> nrf_dfu_flash: Initializing nrf_fstorage_nvmc backend.
0> <debug> nrf_dfu_settings: Using settings page.
0> <debug> nrf_dfu_settings: Copying forbidden parts from backup page.
0> <debug> nrf_dfu_settings: Destination settings are identical to source, write not needed. Skipping.
0> <info> nrf_dfu_settings: Backing up settings page to address 0x7E000.
0> <debug> nrf_dfu_settings: Destination settings are identical to source, write not needed. Skipping.
0> <debug> app: Enter nrf_bootloader_fw_activate
0> <info> app: No firmware to activate.
0> <info> app: Boot validation failed. No valid app to boot.
0> <debug> app: DFU mode because app is not valid.
0> <info> nrf_bootloader_wdt: WDT is not enabled
0> <debug> app: in weak nrf_dfu_init_user
0> <debug> app: timer_stop (0x20005980)
0> <debug> app: timer_activate (0x20005980)
0> <info> app: Entering DFU mode.
0> <debug> app: Initializing transports (found: 1)
0> <debug> nrf_dfu_ble: Initializing BLE DFU transport
0> <debug> nrf_dfu_ble: Setting up vector table: 0x00072000
0> <debug> nrf_dfu_ble: Enabling SoftDevice.
0> <debug> nrf_dfu_ble: Configuring BLE stack.
0> <debug> nrf_dfu_ble: Enabling the BLE stack.
0> <error> app: Received an error: 0x00000003!