Made rank 20 in recon slayer but didn’t get skin??

I grinded recon slayer for a week to make 20 and did, but when the challenge came out it would not unlock. Now it is gone and I don’t have my skin? Wtf I want my -Yoinking!- skin 343!! I want a dev to see this -Yoink-!

It was stated multiple times that if you got to rank 20 before Season 4, you had to just start searching for a match in the playlist for it to unlock.