I'm not able to translate the text of one player in the Alliance Chat How can I solve this?

If it's just one player, that means he is writing in a language that is not the language he set in the game.

Example. My game is set in english, if I write in english, you can translate it in your language, but if I write in Italian, you won't be able to translate it in game.

To solve that, the player should change his language in game settings.