The French localization file has some lines commented out; but those lines contain a line break. The string terminator is on a second, unquoted line, which causes lua errors in the file. See e.g. lines 55-56 in Localization.frFR.lua.

The in-game lua error is:

25x InstanceAchievementTracker\Localization.frFR.lua:56: unfinished string near '",'


Locals:

Resolved.