How can I get achievements to unlock after 3 days?

Hi! I'm Rostom, an Independent Advisor. I will be glad to help you here.

Sorry to hear about what happened. Does the issue of unlocking your achievements only happen to this game?

Have you already tried to remove your profile and add it back to your console to refresh your account data? You could also attempt again to unlock it.

If still no go, please visit the guide through this thread https://answers.microsoft.com/en-us/xbox/forum/...

As our last resort, you may file a bug by reporting it through the Report a problem app on your console. Check your guide here https://support.xbox.com/en-US/help/account-pro...

There have been issues lately with achievements not unlocking right away. I had one unlock 2 or 3 days after I achieved it so I say be patient. Also you can try https://www.trueachievements.com/a214675/media-baron-achievement?showguides=1 and read comments
in the solutions to see if anyone else encountered this.

So posting on here might get my achievements to pop? I have an unusually unique achievement issue. On January 8, 2015 I had "Done! Unlocking..." On 3 achievements (Knight in White Assassination, Departure, and No Pain, No Gain) after launching Halo MCC after
their Title Update additional achievements. The next day I guess I got Knight in White Assassination and Departure (I say I guess because they are no longer "Done Unlocking..." But they are also MIA (nowhere in my achievements) and 'No Pain, No Gain' is still
stuck at "Done! Unlocking..." 5 days later that one is still stuck and the other 2 are still MIA. Weird.

Some achievements can take up to 3 days to unlock.

Managed to get the level related achievement after redoing the level about 5 more times, but the collectible related cheevo still won't unlock after being stuck at 100% now for 3 days now, sigh...