This has been happening for over a week and every day I have to reset it multiple times back to euros.
Not sure if you've already checked, but when you look at the very bottom of any Etsy page, do you see the correct region, language and currency? Did you check your Account/Location Settings to see if they're still correct? What could also possible screw things up is if you checked another seller's listing last week and changed the ''deliver to'' location for some reason. If you did, go to any seller's listing and change it back to France.
@LeLightFantastique: Are you experiencing this using an Etsy app (which one on which operating system) or via mobile browser or desktop browser (which browser and operating system)? Is it affecting your shop settings or only how you see (your and other shop's) listings?