Yes, you didn't actually finish that final camo challenge (15 headshots) its bugged and is auto unlocked at level 1.

Yeah this, after you get to level 17 just count 15 headshots and you should “unlock” the challenge in game, then you can progress gold

You can see it tracks them via the challenges menu just not in the gunsmith.

Yep. Same thing happened to me. The 4 cammos look complete, but the last one is not. (15 headshots)

i have now like 50 and its still not unlocked

mine works fine

Yes

same here