A friend of mine and I have been experiencing issues regarding achievements being unlocked for Halo Spartan Assault on the Xbox One. The achievement I have been having issues with is the Extra Credit Achievement, it says 100% completed yet the achievement is still locked. Please look into this situation and if someone has a solution please post it here, Thanks!
This is an issue that can affect any Xbox One game, so it’s out of 343’s hands. It’s the first issue described on this official page. The achievement should silently unlock on its own eventually. However, lately it has taken longer than 24 hours for many gamers. Unfortunately, no one has a solution on the consumer end. Hopefully Microsoft will fix this bug.
Hello TF Precision.
As MathGuy42 has said, this is an issue with achievements on the Xbox One. I suggest waiting for some time (it can take a few days to several months, but is usually sooner than later.) Sorry we can’t help you further.