First, congratulations on getting as far as you have. My first guess would be that you did not toggle a bit letting your head unit know that you have a rear camera installed. This would mean that the car the new head unit came out of a vehicle that did not have a rear camera and was coded this way. If you kept your original coding (as recommended in the DIY), you could see what is different from the new coding and look there. When this guy did a rear camera retrofit, he mentioned having to toggle a bit, but didn't mention which one. https://forums.vwvortex.com/showthread.php?7567066-Golf-OEM-Rear-View-Camera-Retrofit-Success! I would check, but not really interested in going out in the garage, hooking up Vag-com and searching for what bit it is. Maybe in a day or so. Not sure if on OBDeleven Pro if you can select a bit and then there is a drop down that shows features to change such as "reversing camera installed"?
I have had the "park pilot currently not available" when for some reason my car did not recognize. It has happened a handful of times in the going on six years I have had the car. Cured by a hard reset.
To my knowledge it's enabled, I've attached the screenshots from OBDeleven. EDIT: And I did go back and check my old code byte by byte, there are some differences that aren't accepted but I was able to get most things working like the GTI logo on the startup screen (and the correct car in the menu).