Configuration interface not working

[github-k8n]

Updated both RPis using the "hold button on pi" method and tried with both self-compiled uf2 as well as 0.62 prebuilt image. Things seem to work, it still switches back and forth between the monitors, but it does not react at all to the configuration "Left Shift + Right Shift + C + O" , no reboot, no USB mass storage device, no blinking...