It's hard to guess with zero information. Does the trainer find the process? You can see at the trainers main page at the bottom, it will say "Status: Waiting for" or "Status: Found". If it does not find the process then you might have launched a DX9 version or anything else except the trainer is looking for.
If it does find the trainer then you might tell me if you hear any sound when pressing F1. If not, have you accidently turned on the controller mode?
The possibilities are same as if you tell the doctor "It hurts, why does it hurt?" he can try to start from A to Z of the medical problems or, you going to tell him what exactly hurts and what has changed.
When i launch the trainer it says "Status: Waiting for" then i go to steam and launch the game. After the game is launched the trainer stil says "status: waiting for, do i have to go into the main folder of the game and launch the dx11 version, or is it enough that i launch the game from steam?
Hope this is better information.