Continued Rejection After Providing Proof

I have two (2) credits I'm trying to add to a movie that was made a decade. They're "uncredited" credits. I have written permission from the Producer-Writer-Director to add these credits. I supplied the email with that exchange between myself and the rights owner. IMDb keeps rejecting the submission of these two credits. There's no other higher authority that I can ask permission from. Why does IMDb keep saying "We can't verify" this information when I've provided the necessary documentation? Any advice or help will be greatly appreciated.