Have a DZPD3-2BW which I just can't get to include on my C-7. It is really unhelpful that Leviton have such similar part numbers, and don't distinguish them on the device label anywhere; but I believe that's what it is. I also have some number of earlier dimmers such as DZPD3-1BW which included with no issues. I think the distinction is that the earlier devices are plain z-wave and not z-wave plus.
I assume the -2BW device is getting hung up with secure pairing, though I can't really tell as the hub shows absolutely nothing happening. I believe I did get the dimmer to exclude from my old Vera controller, and have also hard-reset it since then.
I suspect the answer is just to be patient and wait for further z-wave tweaks to the C-7, but post here to see if anyone has the same issue...