Created bootloader for CycloneV SOC doesn't work

Hi,

I'm currently trying to follow up several tutorials on creating a preloader and bootloader for an Intel Cyclone V Soc. For example I did all steps from this tutorial:

https://www.youtube.com/watch?v=vS7pvefsbRM

After creating the preloader and bootloader in EDS Command Shell ("make" and "make uboot")

I transfer it to the FAT partition on my SD card drive G:

( "alt-boot-disk-util.exe -p preloader-mkpimage.bin -a write -d g" and "cp uboot-socfpga/u-boot.img /cygdrive/g")

But when I put the card into the Terassic DE 10 Nano Board it will not boot.

I see the following output in Putty:

U-Boot SPL 2013.01.01 (Oct 06 2020 - 09:13:30)
BOARD : Altera SOCFPGA Cyclone V Board
CLOCK: EOSC1 clock 25000 KHz
CLOCK: EOSC2 clock 25000 KHz
CLOCK: F2S_SDR_REF clock 0 KHz
CLOCK: F2S_PER_REF clock 0 KHz
CLOCK: MPU clock 800 MHz
CLOCK: DDR clock 400 MHz
CLOCK: UART clock 100000 KHz
CLOCK: MMC clock 50000 KHz
CLOCK: QSPI clock 3125 KHz
RESET: WARM
INFO : Watchdog enabled
SDRAM: Initializing MMR registers
SDRAM: Calibrating PHY
SEQ.C: Preparing to start memory calibration
SEQ.C: CALIBRATION PASSED
SDRAM: 1024 MiB
ALTERA DWMMC: 0
reading u-boot.img
reading u-boot.img


U-Boot 2013.01.01 (Oct 06 2020 - 09:22:09)

CPU   : Altera SOCFPGA Platform
BOARD : Altera SOCFPGA Cyclone V Board
I2C:   ready
DRAM:  1 GiB
MMC:   ALTERA DWMMC: 0
*** Warning - bad CRC, using default environment

In:    serial
Out:   serial
Err:   serial
Skipped ethaddr assignment due to invalid EMAC address in EEPROM
Net:   mii0
Warning: failed to set MAC address

Hit any key to stop autoboot:  5  4  3  2  1  0 
reading u-boot.scr
** Unable to read file u-boot.scr **
Optional boot script not found. Continuing to boot normally
reading zImage
** Unable to read file zImage **
reading socfpga.dtb
** Unable to read file socfpga.dtb **
ERROR: Did not find a cmdline Flattened Device Tree
Could not find a valid device tree
SOCFPGA_CYCLONE5 # 

I checked all steps but I didn't find the issue.

Can someone help me?

Thank you very much.