unable to boot from SDCard

[dukla2000]

That exact what i tried, but.. on HDMI on my 4k-Monitor never seen a signal, tho whole time, is it possible, that some Monitors are not function?,  the screen become black, but no char's on it. Is it possible, that there is an other component Boot before SDCard?

Conceivably your SPI is corrupt - you could try disabling the SPI while you boot (next entry in the wiki)?

If you are not sure your monitor will work that is a slight concern - I would expect most do though. But equally if you try something like an Armbian image then you should see activity on the on board LEDs as well.

The boot sequence is documented here: conceivably you could try rebuild a bootable eMMC via OTG mode but I think trying to get a bootable SDcard would be my first choice.