I didn’t get Heloskrill

So for days and weeks I was trying complete ever halo game on legendary and to get Heloskrill eventually I managed to complete every halo 1,2,3,4 on legendary I got the achievement but when I login halo 5 I check my armor and helmet and it wasn’t there so I was really upset then I thought to my self is this some sort of glitch or something cause I really disappointed… 343 if you have time to read this I would appreciate the help cause I don’t know what to do.