I currently have one thing in my cart, Fantasy General II - Prologue. It is free but the Pay for your Order Now button is grayed out. I have never had this issue 'buying' free games from GoG before. What am I doing wrong?

The irony that the solution is to wait for a solution is salty and bitter, but thank you.

It seems to work now.

You can buy it as a gift and redeem the code you'll get. Worked fine for me.

So, an interesting follow up. After reading in this very thread that FG2 could now be 'bought' I added the new UnMetal demo to my cart (which still had Fantasy General II) and, again, the buy button was grayed out. I removed the UnMetal Demo and the button went back to normal and so I claimed the FG2 demo. I then readded UnMetal's demo and the button still worked.

So it looks like you can get them both separately, but not together.