This is because Innersloth have decided not to actually support the platform we bought the game on. This time tomorrow will be a week since I contacted them the second time about the problem and I haven't heard back yet.
If Steam is an option for you (it isn't for everyone), you can claim a Steam key from the game's download page and use that version of the game instead. Obviously not a solution for people who specifically bought on itch.io because Steam isn't an option, but it might help some people.