Glitch with “customized” challenge registering. Activision Support advised to “keep trying”
Update on this. I found through my own trial and error the solution. Seems even if you get the triple kill or fury kill to activate the next tier of gold camo it will not register or count towards the challenge if you die BEFORE the camo activates. It is not simultaneous with the third or fourth rapid kill or even with being awarded the triple kill or fury kill badge.