My challenge hub used to work so cool, now I have been getting some problems with some challenges this week for the first time.
1st The sticky nade challenge, I got more than the 5 plasma kills on H4 but it did not count.
2nd Killing some AI enemies on Matchmaking Firefigth did not count, the challenge mention Campaign, firefight etc. but those kills just did not count, then I went to campiang and got it with no problem.
3rd I have played a mission with 1 and 2 skulls active but did not get the challenge, solo and coop. (I remember got this kind of challenges with no problem).
Update, I got the skull challenge on Halo reach with no problem at the first try, I couldn’t on Halo CE and Halo 3.
The sticky one works with no problem on Halo 3.