The issue could be that the I2C lines are not connected to the miniprog3.
I suggest you to route the pins on one of the connectors on the kit and then connecting them to Miniprog3 through wires.
Try this and let me know the results.
sorry I did not post an update.
You are right: CSD Tuning will need an I2C communication, which can go through the MiniProg3 SWD lines.
But this I2C cannot use the Debug Pins of the 014008 (even if de-activating debug by SWD).
So other GPIOs have to be used for this I2C, and these GPIOs have then to be connected to the MiniProg3 SWD lines.
My goal was to re-use the existing Debug Pins already connected to the MiniProg3 for programming. So I could spare GPIOs, and use the Debug Pins for programming or CSD Tuning. No luck.
Thanks for your help.