Rock Pi 4C Plus not booting from MicroSD card?

I just have purchased a brand new Rock PI 4cplus device and wanted to boot from MicroSD card (which is working in a Raspberry Pi) but unfortunately the Rock Pi4 does not boot at all, there is only a

constant green light.

I tried several different MicroSD cards which are all functional and

work with RPI, but no luck with the Rock Pi4 device.

I booted into MASKROM mode and used RKDevTool v2.86 under Windows11 to read

info regarding flash and chip with no success. I therefor assumed that

there is no bootloader on board and flashed the latest bootloader

rk3399_loader_spinor_v1.20.126.bin.

When I again power-up the device with using MicroSD card, again not boot at all.

What can I do to fix this situation?

Hello, there is no eMMC onboard. So it cannot use RKDevTool.
We suggest you to follow this booting guide for second try.
https://wiki.radxa.com/Rockpi4/install/microSD