Oh, you're right. I get the same error on my end if it isn't real money. Do you mind if I suggest an alternative for you? because you could also access demo plays at print studios' website, see: https://www.printstudios.com/games
You can sell them in secondary markets like opensea, blur, magic eden, etc.
Ideally, it follows rollbot (rollbit NFTs). But utilities need to be more solidified partnered with great marketing. Ofc, it's not gonna happen overnight but they are cooking.