The advice is : don't use é, è, ç or à in the name of your Scenario. You'll be able to play it but you won't be able to edit it anymore : the map will look empty in the Editor while actually it is not. You'll have to change its name in ...\Documents\My Games\FieldOfGlory2\Campaigns to be able to edit it again in the Editor.
I guess it is because of the AZERTY keyboard French use (but that FoG2 does not handle) :
Here is an example :
I created a scenario named 'Pasdeé'.
The name of the file is Pasdeé on my hard disk :
It is 'Pasde' in game and 'Pasde?' in the Editor (see below) :
I can play it :
but I can't edit it as it looks empty :
To be able to edit it in the Editor, I simply have to change its name without any é, è, ç or à.
PS : Likewise in P&S.
Voilà !