It means the DLL injection has failed. This can be caused by you have/had CoSMOS or CoSMOS attached to the game. Or because you previously tried activating the trainer and ith as failed. Or because an AV is blocking the injection. Or because the game is frozen while you try to activate the trainer.
I suggest you close game and trainer and wait a few minutes and then try again. If the error still appears please check if you have the C++ redistributables installed (readme).
I deactivated the AV again and downloaded C++ redistributables but I still get the same error message. I have never used the CoSMOS or CoSMOS. And I'm sure the game was not frozen. But I can't get the trainer working.