after finishing all 8 missions of the hundred year war campaign, I didnt unlock the achievement on steam. The same goes for the dont loose a canon achievement in the battle of Formigny mission.
However, i recieved both achievements ingame.
So far, i played the battle of Formigny 3 times. During the first try, I made a manual save, during the next two runs, I didnt because I read about a bug regarding achievements and manual saves, but this didnt unlock them either.
I dont know if this is important, but my first two runs were before yesterdays server maintenance, my third try was today.