Can't activate "King's Quest: Season Pass" even though I've already activated "King's Quest Collection"

[Errant AI]

As the title says, I'm unable to activate King's Quest: Season Pass, despite already having "Kings Quest Collection" activated. (Both from the Humble Sierra 3rd Bundle)

I get the error message:

"The product code you've entered requires ownership of another product before activation.

If you are trying to activate an expansion pack or downloadable content, please first activate the original game, then activate this additional content."

"King's Quest: Season Pass" is the only key in the bundle giving me issues.
I've confirmed that "Kings Quest Collection" activated properly and is in my library.

Any suggestions?

[Errant AI]

I found my solution. I had to go to https://store.steampowered.com/app/345390/Kings_Quest/ and click "Play Game" under "Play King's Quest" After doing so, it allowed me to activate the key. It'd be nice if the requirement is free to automatically add it to your library, but such is life.