Can not boot into NextBox

NextBox
#1

Hello,
other boot topics got resolved or are a bit different, so I’m presenting my case.
I’ve shutdown the NB to change the internet cables and after that it never booted again. I get the same light as Stuck in I dont know what mode?! - #2 by daringer, that dimmed blue for the first minute or two, and inside I see on the Pi mainboard a constant red light and green light that blinks 7 times in a row, then shortly pauses, and repeats.

I tried to plug the power to both usb-c ports, no success, Internet cable blinks.

Any Ideas, how to resolve this?

Regards,
Matej

#2

Ok, there seem to be strange things and strange things.

I played with it for a day, did everything my mind produced, nothing. Checked all connections, replaced al cables, really everything.

Today I tried again, and it works.

I have absolutely no clue.

Thank you anyway.
Matej