I came across this after browsing through itch and finding the game. I followed the project years ago when it was called King Under The Mountain, but kinda drifted away because it was still in development and not really playable at the time. And even though your thread is from months ago, I figured I'd help clear the confusion. Back in late 2023, the publisher they had been working with decided to back out last minute, leaving them to try and publish it themselves. Sometimes its possible, but unfortunately the publisher had demanded they keep the game basically a secret while they worked on it, so by that time no one really knew about the game. Poor launch sales on Steam weren't enough to cover even 1 persons salary, so as of January 12, 2024 the entire staff was laid off and the company wiped to pay off debts. Your emails aren't being answered because there's no one left, and the Steam Key didn't work because they removed it from Steam. Yes, $20 might've been wasted(with the company not existing anymore, I don't think anyone's able to remove it from Itch), it was not wasted on a lazy team of half-competent workers, but rather became a stepping stone on a climb to greatness that was cut short just before the finish line.
I'm hoping this offers any sort of consolation, and I will attempt to reach out to Itch.io staff to see if they can remove the game from the website so that others don't purchase a Steam Key for a non-existent product.
The good news is, the original developer released the game for free on Github so that it might live on, as well as the original King Under The Mountain
https://github.com/rossturner/king-under-the-mountain
https://github.com/rossturner/mountaincore
Also links to the updates from Steam detailing it all
https://store.steampowered.com/news/app/2370310/view/7217647935762367813?l=engli...
https://store.steampowered.com/news/app/2370310/view/519711143023870664?l=englis...