I'm sorry to hear you're having issues. The Xbox 360 servers are still having issues, last time I checked. Numerous people have been complaining about EXP not counting anymore, issues with achievements popping, and armor either not unlocking or disappearing all together. It's a Microsoft issue, sadly, so there's no telling as to when or if we'll see a fix.
exp isnt counting as of last night, campaign being un-completable and armor is a microsoft issue, reported to them 16 days ago and nothing, we need 343 to tell them about bugs, microsoft and 343 dont care about us, we have been loyal to halo despite not getting a good game for 11 years, i feel like an idiot for all the new gold accs ive bought to test bugs for them, the time ive spent working out whats causing bugs and doing all i can to let these classic games die naturally rather than be left to die because theyre broken. The more i do for 343 the more i realise they dont want help because they dont plan on fixing anything, mcc was their newest game which was left unplayable for 3 and a half years and then had a bandaid patch as a desperate attempt to get the classic fans to shut up so they could focus on making the next game great for one month then die like halo 4 and 5.Exp on halo 3 was fixed 3 weeks ago yet here we are, nothing is counting again.Reach probably has the most stable and respectful population yet you cannot complete campaign on that game.
As of now im done caring,let halo die 343, its been dying since reach,we just need you to fix our games, and for the love of god if infinite isnt perfect i dont think even the decade old minimum classic fans will be sticking around.