This happened when I loaded the game for the first time after the last update, but I had a mostly filled upgrade bar for Godly Statues with no clones working on it, and it wouldn't let me add any clones, saying that I didn't have enough Nations. It needed 49. Since everything on the monuments page should be prepaid, I'm assuming this is a bug.
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In offline mode you can progress until it is almost finished without it being paid but it will only finish, if it is paid.