I have the same problem. I used the trainer when game was released and it worked OK with instructions.
Today updated to latest trainer version and tried it and got game to crash after "trainer activated" sound. I have disabled internet (cable not attached) before activating trainer via main menu.
Still it crashes after trying to launch just like instructed in instructions. Some sync problem popped up as well. Uplay is in offline mode (did not matter Uplay offline or online as long as cable not attached when played game on release). I can't figure out what the problem is. The PC can't be online because I don't have another connection than cable and it's not attached to PC. Steam is not running.
[Edited by tostrand, 10/3/2017 12:32:21 PM]
Do you guys start Uplay in offline mode?
Disconnect your PC before you start Uplay and use the offline key for the trainer.