Sorry, this was being discussed in 2 threads (please don’t do that) so I’ve closed the other one. Yes, to confirm, the address should be set to 0xDFF0 (make sure those are both zero, not capital O but it looks like they are).
Now that the address is correct, the question is why no markers are showing up and, for that, I’m stuck. I wonder whether the driver or some permissions are required. I assume this is a PCI-based parallel port not a USB adapter (that USB ones don’t work for anything).
In general, given the difficulties in debugging these devices when they don’t work, I’d recommend using a LabHackers USB2TTL8 which are portable (USB) easy to set up and still offer great timing.