i was recently playing halo4 and i made it to level 19 and then i used th day1 classified code and level up to 22 and didnt get the achievement for reaching level 20.
if you know a way to fix this or assign the achievment to my account that would be great.
Hello g0that way.
This achievement usually unlocks at a future rank-up. Generally, this is the next level up that you unlock following EXP earned from a game, most likely SR23 in your case. However, it occasionally requires further ranking up before the achievement pops. 