I developed the code for my application using Nucleo F446Ze. I use CubeMX and gcc on macOS. All works fine.
Next I want to develop my own PCB with the same processor. Thinking ahead to how I will flash it, I broke off the STLINK and practiced connecting it up back to the Nucleo and programming with the SWD connector (CN6 on the STLINK). This also works fine so I think I know how to connect with the STLINK.
I now have my new PCB. Voltages look good. Current draw is 14 mA. I connect the same STLINK but it does not work. The multi-color LED is Red and never blinks. After copying the bin file to the mounted STLINK file system the following message appears in FAIL.TXT: The interface firmware FAILED to reset/halt the target MCU.
Can anyone expand on exactly what this means? I agree it is probably my new board but I do not know where to start looking.