Same here. I received a receipt and the store record for the game recognizes it as "In Library", but it's nowhere in my library and can't be selected for download. I'm guessing this is just servers past capacity, but it's frustrating that basic stuff like this is broken. I've never purchased a title via Steam and had it not show up in my library for an hour+.

(To be fair, it seems like Steam is down right now as well, so maybe GOG gets a pass.)

Hmm... I don't know this helped me but I closed GOG through Task Manager and launched it again. And suddenly my CP appeared in library. Downloading right now :)