Valve banned 100% discount
The developers of Armillo on Steam released their game for free, hoping to set a price for the game in the future and start with a 100% discount, they contacted Valve and learned that it was no longer possible to do a 100% discount. at all. The developer indicated that this is a recent change to Steam policy.
origin: https://steamcommunity.com/games/349520/announcements/detail/2763474378278517327