I have played around with a Geforce GTX 1050 Ti in the PCIe port but did not manage to use it with nouveau, so I have removed the card from the mother board again.
Now I can see the boot process via AST at my display until it finishes (progress bar at them bottom) and then the screen becomes black.
Obviously also no operating system is booted automatically (after the usual 10 seconds timout) - playing with the cursor keys and pressing enter does also not have any effect.
How can I diagnose this or reset petitiboot?
I have not changed any Blackbird firmware so it should work OOTB...
Edit: I have already tried the usual cold boot (power off) and unplugging any devices (PCIe and SATA)