Shipping Confirmation file error

Hello,

I am trying to upload shipping confirmation file but i am getting below error :

26 Error An internal error occurred. Please try again later.

Do you have any idea what is this ? I am following the amazon instructions on how to fill the file exactly. Filling all mandatory fields (order id, courrier code, ship date, tracking number and ship method) leaving others as empty and paying attention all the formats. What i am missing ?