Me and my friend were playing Halo: CE on legendary. As we were completing the missions, achievements were not being unlocked, despite the campaign status showing completed on legendary. MCC shows all missions completed on legendary but still no achievements unlocked/received. Help! Is this a bug? I can provide screen shots to confirm.
You have a skull activated x0.00% value?
If you have activated some, the mission begins again but with no skull and legendary enabled, just start the mission and press save and quit. Repeat this process with all missions, if they will not give to be an error by not solve …
Sorry for my English, I use the Google translator 
Do I do it in co-op or single player?
In Co-op 