Physical connector mapping
If everything ckecks out during the first test, you can verify a last item:
Turn the power off, then remove the sdcard from the DE10 motherboard, and turn Pauline back on.
All the floppy IO pins should be high.
If that's not the case, something's wrong with the pull-down resistors. It's very important to check those in order to avoid unsollicited writes and other damage during the bootup phase (the first 200 milliseconds needed for the fpga initialization).
In order to do this, check the voltage on your power supply, and on each of the pins on J3 (host) and J4 (drives).
The voltage on the pins should be the same as the PSU's voltage (5V +/- 0.3V) for all pins, except 33, 31, 29, 27, 25, 23 and 21 which should read 0V.
Everything's OK, let's move to the next step…