I don’t remember the exact message from the USB blaster, but it was always identical, did not change when the board was powered or unpowered.
Also, the light at the USB blaster was lit up when I connected everything. After the error message, the light went out until I replugged the blaster at the USB side.
In the OSSC, there was nothing lighting up at any time, except the LCD backlight when I touched the transistor on the bottom side, the backlight was faintly lighting up. I guess the FPGA tri-states its outputs.