You might have actually helped ME out, by giving me an interesting error code to search up on leddit. According to this thread, there should be a way to manually put the "action manifest" for the game in it's right place, which steamvr currently thinks it is not. This might be what my issue is with having steam accounts this game just doesn't work on.
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seems to have at least a work around solution. But like I've told a couple other people, try making a new steam account and running the game lol. If it works, it means it's not just me and I have some big hints as to my own issue, if it doesn't then I dunno why tafuk steamVR can be so fundamentally broken sometimes.
The issue is in finding out where said action manifest file would be for a non steam game, because the solution says to go to the common folder and click the game name, of which non steam games don't get, IIRC they get some random numbers. I had to go through that to find out where the screenshots are stored for heat when you take them through steam, which was a big hassle. It might be possible there's a method to the madness, but I haven't come across the way to decipher what game has what number.
Can you attach a picture of the error code? When does it occur, and what state is the game in when you get the code, and potentially after it?