Vol Polloi III Seasonal Challenge didn't unlock

Hi everyone,
I completed 3 full Campaign Playlists to unlock “Vol Polloi III” but I have unlocked only “Vol Polloi I” and “Vol Polloi II”.
Yesterday I played Halo 3 “Wheels, wheels, and more wheels” playlist (got “Vol Polloi I”) and “Mixin’ it up” playlist (got “Vol Polloi II”). Today I played Halo 2 “Fan favorites” playlist and “Vol Polloi III” didn’t unlock. What’s strange is that it was my first Halo 2 playlist and the game gave me the achievement but not the challenge. Moreover, I played all the playlists in split-screen coop sessions and the game kept track of the number of the mission I played correctly, in fact “Elite Company III” Seasonal Challange counter went from 9 to 13 as it should.
Can someone help me, please? Has the same problem occurred to anybody? Do you suggest me to complete another playlist hoping for the best? Thank you.

Edit: I completed another Campaign Playlist and “Vol Polloi III” unlocked as intended :slight_smile: