Halo CE Legendary glitch

I have recently been going through the halo mcc and i have been playing combat evolved onlegendary mode with no skulls and i have not been reciving any of my achivements, i have gone back and checked if its said i have completed the missions on it and its saying i have

Just give it some time. Sometimes it’s taken 30 minutes, hours, or even days to pop achievements. Nowadays it’s like 30 minutes or so when there’s Live issues.