steamdb.info/patchnotes/6249234/
Looking at the files, looks like they recompiled the whole game. It probably was 64 bit at one point or the trainer would not work for previous versions. Last patch was after the trainer so it may need and update.
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The newest trainer still has this issue. The game was last updated in february, but the trainer that was released 2 days ago still gives the error that it'll only work with a 64bit app.
This is coming from a clean installation of both the trainer and the game (neither of which had been downloaded or installed before yesterday).
Don't have it so I have no idea, ask the trainer maker.
I have just message -DEViL- explaining this exact issue of the trainer failing because it wants you to use the nonexistent 64 bit version letting him know about the issue that the game is a 32 bit and has never been 64 bit.....