Help! Didn't get Achievement for playing 1066 through 1453!

[Heavenly Serpent]

Basically, exactly what the title says. I did not earn the achievement for playing from the 1066 start date to the 1453 start date. I have an Ironman File I can post if it helps. Please help me figure out what the matter is, because I earned several other achievements this run, and do not know why I couldn't get this one!

 

[Aardvark Bellay]

Disclaimer : I'm not tech support. Just another forum member.

Basically, exactly what the title says. I did not earn the achievement for playing from the 1066 start date to the 1453 start date. I have an Ironman File I can post if it helps. Please help me figure out what the matter is, because I earned several other achievements this run, and do not know why I couldn't get this one!

As it is now, it might be an ironman file, but not an achievements compatible one, as the latter would be encoded and impossible to unpack,
while this one can be unpacked and isn't encoded.
So at one point the save apparently got achievement incompatible.