ASSASSIN´S CREED BROTHERHOOD MEGA TRAINER 1.021.03 - Can'not Use for Steam Version, and I so Sadly, Help Me Plese.
Usually when a trainer do not work right away I:
1) Run the trainer as an administrator
Right click on the trainer executable (xxxx.exe), go to
Properties, Compatibility and tick the last box at the
bottom, Apply and OK. It should work now
But if not, continue with 2).
2) Do the same as "1)" with the game executable.
That should fix it, but for more and better information go to: Link (Trainer Troubleshooting Guide)