Out of curiosity, which game?
I promise I am not asking as a gotcha. Just genuinely curious.
I don't play many new games on PC (normally I play recent games on consoles). What I play on PC is older/niche games.
I have a couple of oddballs that I could not make work on Proton. Others had weird issues that got fixed over time.
Sometimes there is a fix, such as fiddling with different Proton versions, etc. Lutris makes this somewhat straightforward.