i changed the name of the folders containing  the localization files from "Chinese_Trad" to "tchinese"

(and also in gamemaker

cmn_loc_current = cmn_loc_load_json_folder("tchinese");)

and the localization files wont load in game (it defaults back to english) unless i add a random space in the files and save them

or move files inside the folder to a different folder then move back 

it also happened once before when i put them into the folders after finishing localizing them on crowdin

Try making a ZIP build to see if the files actually get copied in there - cmn_loc_load_json_folder is just a file_find with subsequent file loading so there’s not a lot that can break.