This is an old thread, but I have the same issue. I "edit" the parking option for a domain, the little box pops up like shown above. I fill it out and submit it. Days later, still nothing. I go back and check the "edit" box and it shows nothing like I never entered anything. I used different browsers and made sure that any adblocks are turned off.
I cant believe this is a widespread thing or they would have fixed it or we would hear more complaints.