Happens not that infrequently unfortunately :(. There might be a general thread with a list somewhere but I can't find it right now. The best thing to do is to contact the developer or publisher directly and ask for it since they are the only ones who can make it happen.

Personally, I feel like I overpaid as it is and that it really should still be early access. At least they are updating on GOG right away that also often doesn't happen.