Hopefully this will help anyone still having problems starting the trainer. First I double click the trainer and do not press F1. Then I start Far Cry 5 and shut down the game once I reach the main menu. I Then press F1 and play normally.
I hadn't tried leaving the trainer running yet not activated approach. It had been closed each time before I began my next attempt. Sadly, it didn't work for me. I got the Unknown file version C:\program files (x86)\steam\steamapps\common\FarCry5\bin\fc_m64dll error again.
oh well, had a sparkle of hope for a minute there.
Same thing, trainer cannot find game, message.
In my case i bought the game through Ubisoft, it brings up the Ubisoft window, and then says it cant find the game.
(i did try to buy it through steam, but steam did not show it as a game i could purchase through there).
I had the same problem, what worked for me before running the trainer, ad an exception in windows defender, paused Kaspersky and killed all uplay processes via Taskmanager. After that it worked without a hitch even though I had multiple monitoirs, odd install dir and uplay in online mode