STM32H7 duble core debug to No device found on target.

[ASche.5]

I have been trying to get the debug setup running in CubeIDE 1.16 according to : dm00629855 Getting started with projects based on dual-core STM32H7 microcontrollers in STM32CubeIDE - Application note

And I was able do see the debug break point holding in the main of M7. Then it ended no ware, so I did a retry of the launch group and then "I got No device found on target" from The ST-Link GDB link. Here I am stuck:

 

Also tryed:

Reset the ST-Link and the USB tree and the Port numbers of GDB - this did not help.

Then also the Cube Programmer  not find the device but the ST-Link is there so what did the debug session do to the MCU to be undetectable ?!

 

 

So what could I have done wrong and what can I do to bootstrap ? please help

[ASche.5]

One can bootstrap over boot0, still I am not sure what made the MCU go that stuck though.

[ASche.5]

In the end it turned out that I did not used the SMPS supply. I was trying to port software that was running on LDO from H743. It is noted in the manual to the nucleo board H755 that only SMPS supply will work in default solder bridge SB setup but I overlooked this. So this comment might help some one as blind as me.