Hey folks, quick update here: I refunded the OP’s pledge and notified him of it a couple days ago. We tried troubleshooting with him and were unsuccessful (this was a weird edge case as most backers were able to get into the game). We can’t say definitively whether it was an issue on Steam’s end, with his hardware config, or something on our side—I chalk it up to bad luck.
It sucks that we couldn’t get this sorted before the end of closed beta and we’re working on our processes so that we can be more responsive when users have technical issues that require more extensive investigation and troubleshooting.