The latest trainer for Crysis 3 will not even respond when you press the f1 key. My version of the game is 1.3.0.0. Hopefully there well be a new trainer soon.
please note that the version we use is located at the main menu of the game.
also, note that for many people you may have to alt-tab out of the game and press F1 on the trainer due to the way the game polls the keys.
best,
cal