Error: target voltage may be too low for reliable debugging

[jomaway]

I have an Nucleo F401RE Board where i broke of the stlink part.

Now i try to use this stlink part to programm and debug an stm32f401cc blackpill board.

I works that i can flash my code onto the blackpill mcu (using platformio and openocd), but i always get the following error message:
Error: target voltage may be too low for reliable debugging.

If i try to start a debug session it won't work.

The STM32CubeProgrammer shows the voltage of the board 0,1V.

I connected a 3,3V pin on the blackpill to the VDD pin on the SWD header at the stlink.

Don't know what i am missing here? Maybe someone can help?

[Tesla DeLorean]

Is the BlackPill self powered? Please diagram all the wiring, USB, etc in your proposed implementation

There might be a better place in inject power on the NUCLEO/ST-LINK stub board, you could check the schematic.